Urobilinogens

It can be concluded from the publications of Rohde [2] and Freund and Lebach [3, 4] that it was Ehrlich who first suggested the use of 4-(dimethylamino)-benzalde-hyde in the presence of hydrochloric acid for color reactions with methylketols that was found also to apply to indole derivatives [S]. Auterhoff [6] designated a reagent for urobilinogen, consisting of a solution of 2 g 4-(dimethylamino)-benzaldehyde in 20 percent hydrochloric acid, correctly as Ehrlich s solution. Hence, it is essentially correct to refer to all reagents which contmn these components as Ehrlich s reagent. 

Conjugated Bilirubin Is Reduced to Urobilinogen by Intestinal Bacteria... 

Normally, most of the colorless urobilinogens formed in the colon by the fecal flora are oxidized there to urobilins (colored compounds) and are excreted in the feces (Figure 32-16). Darkening of feces upon standing in air is due to the oxidation of residual urobilinogens to urobilins. 

Condition Serum Bilirubin Urine Urobilinogen Urine Bilirubin Fecal Urobilinogen... 

In jaundice secondary to hemolysis, the increased production of bilirubin leads to increased production of urobilinogen, which appears in the urine in large amounts. Bilirubin is not usually found in the urine in hemolytic jaundice (because unconjugated bihmbin does not pass into the urine), so that the combination of increased urobilinogen and absence of bihmbin is suggestive of hemolytic jaundice. Increased blood destruction from any cause brings about an increase in urine urobilinogen. 

Renal Effects. In a case of chronic phenol poisoning, dark urine and glucose in the urine were noted in a man following intermittent exposure to vapors and solutions of phenol (Merliss 1972). The urine tested negative for protein and urobilinogen. The urine cleared 2-3 months after removal from exposure. Although the exposure concentrations were not reported, the study author stated that heavy odors were often detectable, and that phenol was often spilled on the patient s clothes resulting in skin irritation. Since phenol is absorbed readily from the skin, dermal absorption may have contributed to the systemic effects that were observed. 

Intestinal bacteria convert conjugated bilirubin into urobilinogen. 

A portion of the urobilinogen is further converted to bile pigments (stercobdin) and excreted in the feces producing their characteristic red-brown color. Bile duct obstruction results in day-colored stools. 

TNB. Elevated levels of urobilinogen were found in all workers exposed to 1,3-DNB indicating hemolysis (Okubo and Shigeta 1982). Limitations of the study are that data were collected 10 days after exposure and information is lacking on the dose of 1,3-DNB. 

Workers exposed to 10-2 00 ppm complained of lacrimation, dizziness, insomnia, vomiting, constipation, and anorexia liver tenderness on palpation, epigastric pain, and elevated urobilinogen were observed. Impairment of the central nervous system and increased morbidity, especially diseases of the liver and bile ducts, were found in workers chronically exposed to ethylene dichloride at concentrations below 40 ppm and averaging 10-15 ppm. ... 

Phenothiazines may increase serum cholesterol, spinal fluid protein, and urinary urobilinogen levels decrease protein bound iodine yield false-positive urine bilirubin tests interfere with urinary ketone and steroid determinations. 

Drug/Lab test interactions False-positive tests for urobilinogen may occur during nizatidine therapy. False-positive tests for urine protein with Multistix may occur during ranitidine therapy testing with sulfosalicylic acid is recommended. 

Lab test abnormalities Aminosalicylic acid has been reported to interfere technically with the serum determinations of albumin by dye-binding AST by the azoene dye method and with qualitative urine tests for ketones, bilirubin, urobilinogen, or porphobilinogen. 

Within the intestine, bacteria convert bilirubin to urobilinogen. 

After it has settled, if the bottom layer is pink, the sample is urobilinogen positive and PBG negative. Grade the color intensity (trace, 1 +, 2 +, 3 +, 4 +) and record the results. 

A negative and positive control sample (pooled urine, spiked with urobilinogen/ PBG) is run with each batch of patient samples. 

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