The concept of the urine test and specific reaction of the urine in various diseases according to Enrico Cauchi – member of the medical council of Malta (1933)


The Study of urine from the outset has always aroused the interest of scientists and physicians all over the world, from ancient Greeks and Romans to Hindus, Hulcos in Mexico, Australian native etc.

The urine in such case was considered not only as a waste product but also as a therapeutic product.

In the late XIX century scientific knowledge had already identified the function of substances that favor the increase of urinary output, and physicians over the centuries have always tried to analyze urine in various ways.

In Cauchi’s work in 1933 all chemistry and pathophysiological knowledge of the time was condensed. Cauchi signed the preface as Member of the medical council of Malta.

He was a medical doctor of the early20thcentury, He wrote about the physiopathology of urine ranging from chemical and physical behavior, to the analysis of sediments and the special reactions of the urine in various pathologies. In particular Cauchi emphasizes the main diseases of the time combines the behavior of the reaction of urine as a diagnostic and prognostic instrument, stressing the importance of the urine test and describing the method used for analysis at the time.

The analyses of the text in the issue seems to belong to archaic medicine, and it is difficult to think today, that what was presented as very “up-to-date- science” at that time, took place only 80 years ago.

Reading the full original text with today experience we are led to consider the increasing importance that scientific community gave in the past, and still gives to urine test.

Key words: Cauchi Enrico, Down Brothers’s test, Urinacidimeter, Urine Test



The Study of urine from the outset has always aroused the interest of scientists and physicians all over the world, from ancient Greeks and Romans to Hindus, Hulcos in Mexico, Australian native etc.

The urine in such cases were not also to be considered only as a waste product but also as a therapeutic product [1].

Late in XIX century, scientific knowledge had already identified the function of substances that favor the increase of urinary function [2], and the physicians over the centuries always tried to analyzed the urine in various ways.

Enrico Cauchi, member of Medical Council of Malta, was a Physician of the early XXth century who wrote two books entitled: “Physiology and pathology of urine” and “Pathology of the urine” belonged to the “Opera medica” edited by A.Wassermann & c. (October 1933), and consisted of three tomes (Figure 1).

In general Cauchi describes the Urine test as a vital aid to gain information about the state of the kidneys, of the bladder, of replacement of materials(excretion of metabolites), heart strenght and diseases of the other organs, through the presence of internal heterogeneous substances in urine. He also describes and in many case designed laboratory instruments in use at that time.

In the second part of the first book we found a chapter, the fifth, entitled: “Special reactions of the Urine” where Cauchi dwelt at length discoursing chemical reaction that could have at the same time, diagnostic and prognostic value.

The author consider some variants that at the time the scientific world was testing, trying to have higher and better sensitivity and specificity, describing different types of reactions according to the major diseases of the time.

The urine test

The author skillfully dissects mini paragraphs the text, describing and synthesizing the content of what at the time represented the core concepts of the meaning of examination of urine, analyzing the “urine” in its physiological state where there is no albumin. He also attempts an analysis with the means of the time an several diseases, including patients with “typhoid fever”, “Carcinomatosis”, and generally speaking about various pathological states in wich cylinders and Kidney epithelia begin to appear.

The author, indeed, defines the urine as: “a liquid where urea and uric acid are always present, and in addition the presence of creatinine can assure that it is a urine”.

For this reasons Cauchi describes some methods to identify Urea, Uric acid and Creatinine, matching the supposed liquid with nitric acid for urea, with hydrochloric acid plus nitric acid plus sodium hypoclorite for uric acide, and very important the reaction for creatinine matching the presumable urine with sodium nitroprusside plus acetic acid, and heating finally the mixture to find the the torquoise precipitate of creatinine.

In the scientific technological evolution of the time the author furthermore describes two instruments to evaluate the acidity of urine: the Urinacidimeter and the Down Brothers’test.

The Urinacidemeter (Figure 2) consists of a tube 30 cm long and 1 cm wide,closed at one end and opened at the other, divided in three sections; in the first was placed a solution of water lime, in the second solution of phenolphthalein and in the third pure urine.

Through the use of special tables, defined at the time, it was possible to analyze the acidity of urine expressed in grams of oxalic acid per liter.

The second instrument provided by firm Down Brothers London, consisted of a vertical tube 30 cm long and 1 cm wide (Figure 3),closed at the bottom and opened at the upper end with a glasscap, divided into two parts, one to contain 10cc of urine, the other with a double graduation for a decinormal solution of sodium hydroxide in the left side, and for the corresponding percentage of hydrocloric acid in the right side. As reported by Cauchi although these instruments did not give perfect results, they were however useful for a clinical response.

In Cauchi’s book the presence of uric acid was not only important to identify the urine as such, but also to investigate the quantitative excretion of uric acid describing various method more or less reliable and accurate and according to him as the best Ruhemann’sUricometer (Figure 4).

Before speaking of the uricometer, it is interesting to specify that the author dedicates a very long chapter of the book to uric acid (twelvepages), possibly for the importance that the gout had not only in the past [3] but also during his time.

Infact he deduced that the production of uric acid is strictly connected with the typology of the ingested food and that purinic basis together with uric acid constituted purinic bodies.

He also mentions other scientists of his time and doctors from his recent past like Kunke and Meyer that emphasized an increase of uric acid in leukocytosis or after ingestion of thyme cow.

Furthermore he mentions Moris and Herman who observed an overproduction of uric acid after a meal rich in meat and vegetables.

The Uricometer consists of a graduated test tube, opened in one end with three divisions closed in the other. At the closed one; the lower indicated with “S” the highest with “Y”. The space between S and Y divided into two equal parts. The S extremity filled with carbon disulfide and on the top stratified there is a solution of iodine with potassium iodide. Over these, drops of urine are added and slightly shaked until the carbon disulfide takes a milky complexion. Following this procedure the level of liquid is read in value %.

Cauchi’s interest was also directed in the possibility that through the urine test was possible to diagnose many pathologies like Tubercolosis, Typhus, Pancreatitis and eventually cancer of abdomen. Below there is a list of these.

Reaction of Morits Weisz

The Moritz-Weisz’s reaction, used for tuberculosis, matches the potassium permanganate on urine (gold yellow if positive). On the basis of is report this reaction has a high diagnostic and prognostic value for a series of reasons:

  1. Simplicity and rapidity
  2. High sensitivity
  3. Lack of influence by drugs or by alkalinity of urine
  4. The 60% of positivity in case followed by death (in the context of the preantibiotics era)

Reaction of cammidge in the diseases of the pancreas

The author lists more reactions depending on various diseases that could have a diagnostic value, as is the case of the complex reaction of Reaction of Cammidge for pancreas, with lead carbonate/acetate, in wich the author assert that it appears to be clear and obvious when the “entire pancreas” doesn’t function, rather when only one part of the pancreas is concerned. Cauchi through the analysis of 1465 patients with pancreatic cysts, acute and subacute pancreatitis and other mixed forms affirmed that the reaction had a strong positivity in most cases.

Befor starting with the test, however it was necessary to remove the albumin and eventually the sugar from the urine if contained.

Specific reaction on the urine of cancer patient

At the same time however Cauchi correctly specifies that other author identify the limits of the reaction, declaring to have found positivity in other abdominal diseases of stomach, carcinomatosis and tubercolosis of the peritoneum, intestinal obstruction etc. Justifying the results, saying that “it was impossible to deny that what interests the abdomen in such way, would affects the pancreas”.


In Cauchi’s original textbook the importance of urine test is very stressed.

The Author considers the test not only for diagnosis but also for the prognosis for several local and general sicknesses.

Textually he says that: “The urine test enriches the physician of much practical and theoretical knowledge and enables him to easily understand the chemistry of the organism in abnormal disease processes”; much more “if it is performed, like same physicians perform auscultation and percussion this test could gives important information about chemical disorder in the pathophysiologyof urine.”

At the end another concept appears in the text; the entire pathophysiology of the urinary tract is grouped under the Urology and the Urobacteriology chapter, in the book there isn’t informations about the Nephrology branch of Medicine appeared some years later.

Between the utility and hazards of phosphorus through the centuries


Phosphorus has been shown to be a predictor of cardiovascular mortality in kidney disease subjects. Phosphorus was discovered in 1669 and was considered a philosopher’s stone, it was used as medicament but there were reported deaths after its  use. High serum levels of phosphorus are associated with increased risk for cardiovascular disease in the general population  in subjects free from chronic kidney disease. Phosphorus can be defined as a useful and hazardous element for public health.

Key words: calcification, phosphorus, pollution, public health, Saint Agustine



Phosphorus is a recognized physiologically crucial anion involved in more than one million of metabolic steps in humans and animals with a very fascinating history [1] [2]. During the Roman Empire, when the Romans used to collect large quantities of urine for industrial use, to brush teeth, to attend wounds and to whiten woolen togas;  it is now known that phosphorus is an important component of detergents. Suetonious and Dio Cassius reported the method to collect the urine in Pompei: men walking in the streets of Pompei were invited to give the urine and their testicles were sqeezed if they were not able to urinate [1] [2]. This was clearly painful and the men seemed to howl as do barking dogs hence the word “latrina” from “latrato” (barking). The presence of phosphorus in the nature was reported by Saint Agustine, the Christian theologian philosopher who lived from 340 to 430 AD and noted a perpetual light coming from the sepulchers of early Christians. This is now thought to be the result of the production of self-igniting phosphorus-containing gases arising from decaying bodies [3]. In the 14th century, Achid Bechil and later Teophrastus Bombastus von Hohenheim, the Swiss alchemist known as Paracelsus who lived from 1493 to 1541, mentioned that the distillation urine produced unknown substances [1]. But the clear linkage between phosphorus and urine was reported by the merchant and amateur alchemist Henning Brandt who in 1669 distilling 5500 liter of horse urine obtained 120 grams of a white substance that gave off a white light. He was impressed because he thought that the new substance was the philosopher’s stone expected to turn base metals like lead in gold. The substance was named phosphorus from the ancient Greek phos, meaning light, and phorus, meaning bringing. In the following years numerous alchemists and scientists as Ambrose, Goodfrey, Kraft, Kunkel, Hensing, Gahn and Kramer studied this new substance and its properties [1] [2] [3].

Phosphorus as a medicament

In 1675 Johann Lincke, apothecary in Leipzig, was the first to sell phosphorus-containing Kunkel’s pills to cure colic, asthma, fever, tetanus, apoplexy and gout [3]. Evidence of phosphorus content in the brain was described by Thomas Hensing in 1719 who suggested its relation to mental ability, and in 1730 Kramer considered phosphorus an effective remedy for epilepsy and depression [3]. In 1796, Leroy suggested the use phosphorus for the treatment of tubercolosis at a dose of 3-8 mg/day. In 1817 Annibale Omodei (Figure 1) suggested the use of phosphorus for the treatment of fever, epilepsy and paralysis but treated patients died [3]. In 1825 and in 1854 Pietro Moscati and Glover respectively examined various Galenicals used as medicaments and suggested various doses for phosphorus. In addition, Glover (Figure 2) reported a formulation of phosphorus, chloroform and cod liver to treat scrofula and tuberculosis [2]. In 1876 The British Medical Journal reported the use of phosphorus pills in British Pharmacopoeia (Figure 3) and Ashburton Thompson in his “Phosphorus in Medicine” published in 1874 considered the use of phosphorus in veneral diseases, nervous exhaustion, melancholia, softening of the brain, pneumonia, hysteria, apoplectic paralysis, impotence, migraine, epilepsy, cholera, assorted skin diseases, alcoholism, tubercolosis, amaurosis, cataract, glaucoma, tooth ache and neuralgia [3]. In 1930 a paper published in the Journal of the American Association recommended the use of phosphorus to stimulate the formation of new blood cells and to promote growth [1] [2] [3].

In 1935 a paper of Coltart published in Lancet suggested the use of phosphorus as a nerve tonic. Phosphorus was considered also as good agent to stimulate the cognitive activity [3]. [3]

Phosphorus as a hazardous element

The first real evidence of phosphorus as a hazardous element was reported by Orfila in 1817 when he noted that the injection of phosphorus into the jugular vein of a dog caused sudden death [2] [3]. In 1907 in Germany several women died after the ingestion of solution containing hundred match heads used for abortions  [2] [3]. Phosphorus was used in soup, cake, tea, rum to commit. Mary Wilson was a famous poisoner who murdered two husbands using phosphorus in their foods [2] [3].

During the last World War and in contemporary war conflicts phosphorus was used for making burning bombs which have caused millions of victims. Today phosphorus is still used as toothpaste, fertilizer, detergent, and in water purification form perpetual algal bloom detected in 1950s in the lakes of North America. In 1960, the British Dental Journal and British Journal of Industrial Medicinereported cases of phossy jaw disease in workers in military factories using phosphorus to produce bomb [2] [3].

In 1972, the USA and Canada agreed to limit the concentration of phosphorus to 1 mg. per liter in water discharged into the lakes. This was clear knowledge of phosphorus as responsible for water and air pollution. In 1977, the USA Environmental Protection Agency published recommendations for the use of phosphorus to avoid water and air pollution. Nephrologists in 2000s have demonstrated that phosphorus is responsible for high morbidity and mortality due to cardiovascular calcification in persons with Chronic Kidney Disease (CKD), attributing to phosphorus a key role in the calcification process of the arterial smooth muscle cells [4] (full text) [5] [6] [7] [8] (full text) [9] [10] [11] [12] [13] [14] [15].

Zyad reported that phosphate induced vascular calcification is mediated through the activation of mitochondrial reactive oxygen species and p65 nuclear translocation [15]. Phosphate entry into the cells via Pit-1 or possibly other transport mechanisms and stimulates mitochondrial membrane potential and leads to increased production of reactive oxygen species (ROS). Superoxide and ROS activate the nuclear factor kB (NK-kB) pathway with IkBα phosphoyrilation and subsequent proteasome degradation. The activated NF-kB is then translocated into the nucleus, where it binds to specific sequences of DNA and leads to increased expression of osteogenic transcription factors. The activation of membranous ossification programs leads to phenotypic changes in the cell as well as the release of membranes vesicles and apoptotic bodies, both containing hydroxyapatite crystals [15]. High phosphorus serum levels are strongly and independently associated with a more rapid decline of renal function in patients with advanced CKD [14]. Recently it was hypothesized that phosphorus could be involved in carcinogenesis: as a result a fascinating question arises whether dietary Pi intake modify cancer cell survival in animals and humans. In fact phosphorus alters certain serine/threonine kinases (Akt/protein kinase B), that are crucial regulators of cell proliferation, differentiation and metabolism [16]. It has also been reported that phosphorus is responsible for a chronic low grade of inflammation [15] [16] that could be related with telomere dysfunction via increasing ROS-mediated DNA damage and thus accelerate the accumulation of senescent cells, initiating a circulus vitiosus in which cell senescence aggravated by chronic inflammation, limits tissue regeneration and accelerates ageing [16].


On the basis of the previous considerations the daily intake of phosphorus exceeding 800 mg needed for the metabolic activity in humans is potentially dangerous. Many authors have suggested to reduce the daily quantity of protein originating phosphate but this can predispose to malnutrition especially in CKD patients trated conservatively or chronic haemodialysis [8] (full text) [11].  It is mandatory to avoid foods containing polyphosphates [11] [12] [13] [14]  and beverages containing ortophosphoric acid [11] and drugs containing phosphorus [17]. Now is time to appeal to governments for interventions to abolish or limit and reconsider the use of phosphorus in dietary products. We must encourage CKD patients to adhere to phosphate binder therapy and to personalize their better hypophosphoremic therapy. Phosphorus is a useful element for the metabolic activity in humans and animals but it can become hazardous when it exceeds the serum normal range. We are convinced that it is necessary to redefine the normal range of serum phosphorus level considering the reported increased mortality risk due to cardiovascular calcifications in patients with phosphorus serum levels more than 3,5 mg/dl [18] (full text). Phosphorus has been shown to be a predictor of cardiovascular death in kidney disease subjects and in general community [19].


[1] Bombastus von Honhenheim T (Paracelsus): De Secretis natura misteriis libri decem.1582,Basil, Petrum Perna Editor

[2] Emsley J: The 13th element:the sordid tale of murder,fire and phhosphorus.2000 New York,Wiley Editor

[3] Savica V, Santoro D, Mallamace A et al. Phosphorus: the philosopher’s stone discovered in 1669. Journal of nephrology 2009 Nov-Dec;22 Suppl 14:60-3

[4] Giachelli CM Vascular calcification: in vitro evidence for the role of inorganic phosphate. Journal of the American Society of Nephrology : JASN 2003 Sep;14(9 Suppl 4):S300-4 (full text)

[5] Finn WF Phosphorus management in end-stage renal disease. Seminars in dialysis 2005 Jan-Feb;18(1):8-12

[6] Savica V, Calò LA, Caldarera R et al. Phosphate salivary secretion in hemodialysis patients: implications for the treatment of hyperphosphatemia. Nephron. Physiology 2007;105(3):p52-5

[7] Savica V, Calò LA, Granata A et al. A new approach to the evaluation of hyperphosphatemia in chronic kidney disease. Clinical nephrology 2007 Oct;68(4):216-21

[8] Savica V, Calò LA, Monardo P et al. Phosphate binders and management of hyperphosphataemia in end-stage renal disease. Nephrology, dialysis, transplantation : official publication of the European Dialysis and Transplant Association – European Renal Association 2006 Aug;21(8):2065-8 (full text)

[9] Savica V, Bellinghieri G, Santoro D et al. Phosphorus-related mechanisms of vascular calcification. Archives of internal medicine 2007 Nov 26;167(21):2368

[10] Bellinghieri G, Santoro D, Savica V et al. Emerging drugs for hyperphosphatemia. Expert opinion on emerging drugs 2007 Sep;12(3):355-65

[11] Savica V, Calò LA, Monardo P et al. High phosphate content beverages in dialysis patients: relevance for hyperphosphatemia and cardiovascular risk. Nutrition, metabolism, and cardiovascular diseases : NMCD 2008 Oct;18(8):e39-40

[12] Savica V, Calo’ LA, Santoro D, et al: Salivary phosphate secretion in chronic kidney disease.2008,J Ren Nutr,;18:158-164

[13] Dhingra R, Sullivan LM, Fox CS et al. Relations of serum phosphorus and calcium levels to the incidence of cardiovascular disease in the community. Archives of internal medicine 2007 May 14;167(9):879-85

[14] Caravaca F, Villa J, García de Vinuesa E et al. Relationship between serum phosphorus and the progression of advanced chronic kidney disease. Nefrologia : publicacion oficial de la Sociedad Espanola Nefrologia 2011;31(6):707-15

[15] Zyad Al Ali: Phosphate,oxidative stress, and nuclear factor kB activation in vascular calcification.2011.Kidney Intern; 79 (10):1044-7

[16] Jurk D, Wilson C, Passos JF et al. Chronic inflammation induces telomere dysfunction and accelerates ageing in mice. Nature communications 2014 Jun 24;2:4172

[17] Sultana J, Musazzi UM, Ingrasciotta Y et al. Medication is an additional source of phosphate intake in chronic kidney disease patients. Nutrition, metabolism, and cardiovascular diseases : NMCD 2015 Oct;25(10):959-67

[18] Kestenbaum B, Sampson JN, Rudser KD et al. Serum phosphate levels and mortality risk among people with chronic kidney disease. Journal of the American Society of Nephrology : JASN 2005 Feb;16(2):520-8 (full text)

[19] Savica V: Phosphorus: A useful and dangerous element for the general community. pp 99-106 In: De Santo NG et Al: Survival is not enough; for Wordld Kidney Day, 2014, Italian Institute for Philosophical Studies Editor

On the discovery of UREA. Identification, synthesis and observations that let to establishing the first uraemic retention solute


Jean Batiste von Helmont (1577-1644) described a salt that “never occurs outside man’s body”. The substance  was further characterized by Hermann Boerhaave from Leiden (1688-1738) in Elementa Chemiae where he described the whole procedure for isolating it from urine of healthy persons.
The French scientists Fourcroy and Vauquelin, in 1808, named it “urée” whereas Jean-Etienne Bérard from Montpellier established its chemical composition in 1817. The synthesis of urea was accomplished by Friedrich Wöhler (the first organic substance to be synthesized). Finally in 1851 Friedrich Th. von Frerichs introduced the term “Uraemia”.

Key words: uraemia, uraemic toxicity, Urea discovery


Although the discovery of UREA in urine is frequently attributed to Hermann Boerhaave [1], from Leiden, the first description we know of this particular urinary salt is from Jean Baptiste Van Helmont. He described a salt that “never occurs outside man’s body”, that “differs from sea-salt, also present in urine, by remaining unchanged in its course through the body and on putrefaction of urine”, and added “the sea-salt in its cooling, adheres to a wooden vessel even while it is separated from saltpeter, but the salt of urine grows together in the bottom of the liquor” [2]. Jean Baptiste van Helmont (1577-1644), was a Brussels born chemist and physician, founder of the iatrochemical school which looked to chemical explanations of vital phenomena. He was a man of great intellectual curiosity and studied philosophy at Louvain.

The best known text on the description of urea and also on the method for its purification is from Hermann Boerhaave [1] (1668 – 1738), a Leiden born botanist and chemist who greatly participated in the renown of the Leiden University during the XVIIth and XVIIIth century. He wrote in his “Elementa Chemiae“:

“Take some very fresh well-concocted Urine of persons in perfect Health, put it preferently into a very clean Vessel, and with an equable Heat of 200 degrees, evaporate it till you have reduced it to the consistence of fresh Cream” …“Put a large quantity of this thick inspissated Liquor into a tall cylindrical glass vessel with a paper tied over it and let it stand quite in a cool place for the space of a year…”

“By this means, then, you will have a solid, hard, sub-pellucid, brown saline mass, fixed all about the bottom of the Vessel; and over this, a thick, black, pinguious liquid, separated and rejected as it were from the concreted Salt …”

“Decant, take out the saline mass, put it into another Vessel, pour some very cold water upon it and shake it about to free it from its oily Impurities which may be done pretty easily, as it will not readily dissolve in cold Water…”

“Keep this saline matter under its proper title.

If this is dissolved in hot Water, and strained till the Lixivium becomes exceeding limpid, and evaporated to a Pellicle in a very clean glass Vessel, then, if you set it by a cold place, it will shoot into saline Glebes of a particular kind, that are perfectly distinct from every other Salt.

In their figure, and solidity, however, they come pretty near to the Crystals of sugar. These are not fetid, nor alkaline but very volatile.This is the native Salt of urine.”

Boerhaave described in detail how urea was indeed in urine (an intrinsic element of a living animal or human being). He already proposed that to obtain urea is preferable to use someone normal and described a method which included steps longer than 1 year, as he left the crude material he obtained urea from for one year in a cool place before he used it.

Fourcroy and Vauquelin [3] in 1808, gave this substance the name of “urée” because it was specific of urine, a product clearly specific of living animals and Bérard in Montpellier in 1817 [4], completed the remarkable description of the chemical composition of urea by William Prout in London [5], following the work by Fourcroy and Vauquelin in France. Jean – Etienne Bérard (Figure 1), reported that the composition of Urea from urine contained 43.4 % of Nitrogen, 19.4% of Carbon, 10.8% Hydrogen, and 26.4% Oxygen [4].

Pursuing the work contributed by the chemists, Friederich Wöhler dramatically changed the view of this substance that was different from sea salt and thought to be exclusively produced by animals when he wrote to Berzelius in Stockholm: “I can make urea without needing a kidney, whether of man or dog. The ammonium salt of cyanic acid is urea” (HCON + NH3 → H2N-CO-NH2). Wöhler had succeeded in the synthesis of urea outside from an animal and established the starting point of modern organic chemistry. Interestingly, Wöhler was upset by his discovery. He wrote to Berzelius, “The great tragedy of science, the slaying of a beautiful hypothesis by an ugly fact.” Vitalism, which proposed that the compounds of the living organisms were unique, submitted to the “life’s spark”and could not be made from inorganic materials, was the dominant thinking in that time in Europe. Wöhler certainly also adhered to this theory and his discovery making an organic compound from inorganic materials was contradicting his own believes.

Physicians greatly contributed to the understanding of the production of urine and urea excretion. Joseph Nicolas Comhaire (1778-1860) observed that when both kidneys are removed from a dog, no urine is accumulated in the bladder, showing that the kidneys are at the origin of the urine [6].

In 1821, Prevost (1790-1850) and Dumas (1800-1884) reported their experiments with dogs that they nephrectomised in the Society of Physics and Natural History in Genève in 1821 [7]. They first explained their observations on dogs:

“When one is to look the physiologic phenomena following the removal of the kidneys, it is preferable to first remove the right kidney, since its connections with the liver, and leave a fifteen days delay between this procedure and the next one. The first one, if it has been well performed does not alter the health of the animal…”, “…When the animal has lost its second kidney is merely affected before the third day…”, “…Finally, all the mentioned symptoms worsen, weakness increases, and the animal dies between the days 5 and 9. If one removes both kidneys at once, the resulting inflammation shortens this time lapse, and the subject seldom goes until days 4 or 5…”

Then they studied the blood and the urine of these animals and concluded that the urea observed in blood was the same as the urea found in urine and indeed, when dogs were binephrectomised doubled the amount of urea in blood: « We have observed that the same procedures on the blood of the binephrectomised animals produced twice as much alcohol residue »… « giving a white and crystalline substance which was entirely soluble in water » which they analysed and compared to the composition reported by Bérard and they concluded as follows: « The difference merges with the errors possible in this type of analyses, and we think that it is permitted to conclude that the urea from the blood and that of urine are identical [7]»

This work set the basis for the “humoral” view of renal physiology, by opposition to “morbid anatomy” theory, supported by Bright and which was dominant in that time in Europe (early 1800). Further work in refining Liebig’s method to dose urea contributed by Joseph Picard (1834-1896) [8] enabled him to see a negative gradient between renal artery and vein: the kidney removed urea, whilst a positive gradient was observed between carotid artery and jugular vein showing that the brain did not. The basis for renal physiology was set.

Friedrich Th. von Frerichs (1819-85) introduced in 1851 the term “Uraemia” and the concept of retention solute when commenting on Bright’s reports [9], and R. Christison [10] and JC. Gregory[11] introduced the putative toxic effect of uraemic retention solutes. Urea has been since, the most frequently used compound to assess kidney diseases and it has given the name to kidney related dysfunction: “uraemia” and uraemic syndrome are what we know presently as chronic kidney disease (CKD), and as such urea deserves a prominent place in the list of compounds known to be altered during renal disease [12]. Urea has not only been used to assess renal dysfunction, but is the most widely used parameter to assess the quality of replacement therapy, although the toxicity of urea is still under debate more than 200 years after its discovery [13].


The description of the discovery of urea is very nicely reported by G Richet in the HISTORICAL ARCHIVES series of Kidney International [14]; very much advised reading.


[1] Boerhaave, H, Vol II, pp 317-318, Process XCVIII «Elementa Chemiae» 1727. English translation by T Dallowe

[2] Van Helmont JB. Van Helmont’s Works. Translated into English by J Chandler. London: L. Lloyd, 1664.

[3] Fourcroy, Vauquelin. Nouvelles expériences sur l’urée. In: Muséum d’Histoire Naturelle. Annales du Muséum d’Histoire Naturelle. Vol 11. Paris. 1808. pp 226-230

[4] Bérard JE. Essai sur l’analyse des substances animales: présenté et publiquement soutenu à la Faculté de médicine de Montpellier, le 9 Juillet 1817. Montpellier: Jean Martel aîné. 1817

[5] Prout W. Observations on the nature of some of the proximate principles of the urine; with a few remarks upon the means of preventing those diseases, connected with a morbid state of that fluid. Med Chir Transactions. 1817; 8: 521-544

[6] Comhaire JN. Dissertation sur l’extirpation des reins. Thèse. Paris, 1803

[7] Prevost JL, Dumas JB. Examen du sang et de son action dans les divers phénomènes de la vie. Annal Chim Phys, 1823;23 : 90-104

[8] Picard J. De la présence de l’urée dans le sang et de sa diffusion dans l’organisme à l’état physiologique et à l’état pathologique. Thèse. Strasbourg, 1856, 96p 

[9] Frerichs FT. Die Bright’sche Nierenkrankheit Und Deren Behandlung. Braunschweig, 1851

[10] Christison R. Observations on the variety of dropsy which depends of diseased kidneys. Edinburgh Med Surg J Tome 32: 263, Oct 1829

[11] Gregory JC: On diseased states of the kidney connected in life with albuminous urine. Edinburg Med Surg J part I, 36: 315—363, 1831 and part II, 37:54—94, 1832

[12] Vanholder R, De Smet R, Glorieux G et al. Review on uremic toxins: classification, concentration, and interindividual variability. Kidney international 2003 May;63(5):1934-43

[13] Duranton F, Depner TA, Argilés À et al. The Saga of Two Centuries of Urea: Nontoxic Toxin or Vice Versa? Seminars in Nephrology 2014 Mar;34(2):87-96

[14] Richet G Early history of uremia. Kidney international 1988 May;33(5):1013-5