Hyperammonaemic encephalopathy associated with retention of urine in multiple large diverticula

Abstract

A 76-year-old woman had been aware of lower abdominal distension for several years and reported having no clear desire to void. The day before being admitted to a local hospital in a coma she had begun to vomit and became disoriented; she also had a lowgrade fever. An indwelling catheter was placed in the bladder and 1 L of urine was drained immediately, but the urine was not analysed or cultured. CT of the brain showed no manifest abnormalities. Serum creatinine levels and liver function tests were normal but the serum ammonia level was high, at 3.77 mg/L (normal <0.75 mg/L). Abdominal CT showed no evidence of liver cirrhosis or portal-caval shunt. Aminoleban1 (an amino-acid preparation for hepatic insuf®ciency; Table 1) and an antibiotic (cefotiam hydrochloride, 2 g/ day) were given intravenously. She became increasingly alert and the serum ammonia level decreased rapidly, reaching 0.52 mg/L on the second day after admission. An examination of serum amino acids showed a normal Fischer ratio (the molar ratio of [valine + leucine + isoleucine]/[tyrosine+phenylala-nine]), which would be expected to decrease in hepatic encephalopathy. No cause for her hyperammonaemic encephalopathy was discovered. A month later she noticed asymptomatic gross haematuria; CT showed a cystic mass in the pelvis (Fig. 1) and she was referred to our department for further examination. Urine analysis revealed sterile urine and no malignant cells; excretory urography showed normal upper tracts. However, cystoscopy revealed many large diverticula of the bladder. The residual urine volume was 800 mL; an indwelling catheter was placed in the bladder, with intermittent catheterization being introduced later. The serum ammonia level remained normal.

Recurring hyperammonemic encephalopathy induced by bacteria usually not producing urease

“…An increase of ammonia levels in blood has been described in different clinical conditions, such as hepatic failure [6], urea cycle disorders, and, rarely, after therapeutic procedures on the urinary tract [1,5,7,8]. In fact, hyperammonemia may be provoked by either a failure of the ammonia metabolism by the hepatic mitochondria, with consequent impairment of the urea cycle, or an increase in the amount of ammonia produced by urease-positive pathogens.…”

“…During urinary tract infections (UTI), urea splitting organisms may determine ammonium production primarily within the urinary system. There are rare conditions when the urine remains into a dilated bladder long enough to allow ammonium reach systemic circulation: this can be due to large diverticula [1], a neurogenic bladder [2] or isolated urinary retention [3,4]. …”

Urea-splitting urinary tract infection contributing to hyperammonemic encephalopathy

“…inborn defects of metabolism and distal renal tubular acidosis), certain types of drugs, Reye's syndrome, porto-systemic shunts, parenteral nutrition, muscular origin, and finally hematological causes such as leukemia. [1][2][3][4][5] Urological causes of hyperammonemia include urinary diversion surgery, UTIs, and subureteric injection for vesicoureteral reflux. In patients with neurological symptoms (such as somnolence and even coma) combined with a UTI, urosepsis should be ruled out as a cause.…”

“…[1][2][3][4][5][6][7] Most urologists, therefore, are not aware of this complication in their patient population.…”

A confused child: Answer

“…Ammonia is lipid soluble and can readily diffuse across cell membranes of the dilated urinary tract and bladder. At a physiological pH of about 7.40 within the venous circulation the equilibrium is overwhelmingly in favour of ammonium formation which is significantly less lipid soluble [1,2]. This mechanism is known as diffusion trapping.…”