Hyperammonemic coma due to Proteus infection

Metabolic Effects of Prostatectomy

Transurethral resection syndrome (TURS), complicating transurethral resection of the prostate (TURP) has been ascribed to hyponatraemia but reports have indicated that hyperammonaemia following metabolism of glycine can be the main cause.

Prospective data has been collected on 96 prostatectomy patients (82 TURP and 14 retropubic). The retropubic group showed no significant postoperative change in the serum sodium or plasma ammonia. Of the TURP group, no TURS occurred although hyponatraemia was noted in 32 patients. The weight of prostate resected, the volume of glycine used, the time taken and the plasma ammonia levels were not significantly different in the normonatraemic or hyponatraemic groups.

In severely hyponatraemic patients (13 out of 32 with a 10mmol/l, or greater, decrease in serum sodium) there was a significant rise (P≤0.05) in plasma ammonia, 1 or 4 h post TURP, which had decreased by 24 h.

There was a highly significant increase in serum glycine level in the hyponatraemic compared with the normonatraemic group (P≤0.001).

There was no correlation between serum glycine and plasma ammonia levels in the normonatraemic or hyponatraemic group.

There were nine patients with post TURP plasma ammonia levels ≥ 100 μmol/l (mean 254) who experienced no mental confusion: six of these patients were hyponatraemic. The weight of prostrate resected (mean 26 g), volume of glycine used (mean 181) and operation time (mean 39 min) were all relatively low.

Subsequently, TURS has occurred in a patient, with severe hyponatraemia and hyperglycinaemia but no hyperammonaemia. This study shows that hyperammonaemia does not always correlate with hyponatraemia or hyperglycinaemia, and high plasma ammonia levels can occur in the absence of TURS.

Hyperammonemia associated with distal renal tubular acidosis or urinary tract infection: a systematic review

BACKGROUND

Hyperammonemia usually results from an inborn error of metabolism or from an advanced liver disease. Individual case reports suggest that both distal renal tubular acidosis and urinary tract infection may also result in hyperammonemia.

METHODS

A systematic review of the literature on hyperammonemia secondary to distal renal tubular acidosis and urinary tract infection was conducted.

RESULTS

We identified 39 reports on distal renal tubular acidosis or urinary tract infections in association with hyperammonemia published between 1980 and 2017. Hyperammonemia was detected in 13 children with distal renal tubular acidosis and in one adult patient with distal renal tubular acidosis secondary to primary hyperparathyroidism. In these patients a negative relationship was observed between circulating ammonia and bicarbonate levels (P < 0.05). In 31 patients (19 children, 12 adults), an acute urinary tract infection was complicated by acute hyperammonemia and symptoms and signs of acute neuronal dysfunction, such as an altered level of consciousness, convulsions and asterixis, often associated with signs of brain edema, such as anorexia and vomiting. Urea-splitting bacteria were isolated in 28 of the 31 cases. The urinary tract was anatomically or functionally abnormal in 30 of these patients.

CONCLUSIONS

This study reveals that both altered distal renal tubular acidification and urinary tract infection may be associated with relevant hyperammonemia in both children and adults.

Severe hyperammonaemia in adults not explained by liver disease

Ammonia is produced continuously in the body. It crosses the blood-brain barrier readily and at increased concentration it is toxic to the brain. A highly integrated system protects against this: ammonia produced during metabolism is detoxified temporarily by incorporation into the non-toxic amino acid glutamine. This is transported safely in the circulation to the small intestine, where ammonia is released, carried directly to the liver in the portal blood, converted to non-toxic urea and finally excreted in urine. As a result, plasma concentrations of ammonia in the systemic circulation are normally very low (<40 μmol/L). Hyperammonaemia develops if the urea cycle cannot control the ammonia load. This occurs when the load is excessive, portal blood from the intestines bypasses the liver and/or the urea cycle functions poorly. By far, the commonest cause is liver damage. This review focuses on other causes in adults. Because they are much less common, the diagnosis may be missed or delayed, with disastrous consequences. There is effective treatment for most of them, but it must be instituted promptly to avoid fatality or long-term neurological damage. Of particular concern are unsuspected inherited defects of the urea cycle and fatty acid oxidation presenting with catastrophic illness in previously normal individuals. Early identification of the problem is the challenge.

Noncirrhotic hyperammonaemic encephalopathy

Adult hyperammonaemia is associated with severe liver disease in 90% of cases. In the remainder, noncirrhotic causes should be considered. Measurements of serum ammonia level must be part of the basic work-up in all patients presenting with encephalopathy of unknown origin, even when liver function is normal. Clinician awareness of noncirrhotic hyperammonaemic encephalopathy can contribute to early diagnosis and the initiation of sometimes life-saving treatment. This review focuses on the physiology, aetiology and underlying mechanisms of noncirrhotic hyperammonaemic encephalopathy and discusses the available treatment modalities.

Clinical practice: the management of hyperammonemia

Hyperammonemia is a life-threatening condition which can affect patients at any age. Elevations of ammonia in plasma indicate its increased production and/or decreased detoxification. The hepatic urea cycle is the main pathway to detoxify ammonia; it can be defective due to an inherited enzyme deficiency or secondary to accumulated toxic metabolites or substrate depletion. Clinical signs and symptoms in hyperammonemia are unspecific but they are mostly neurological. Thus, in any unexplained change in consciousness or in any unexplained encephalopathy, hyperammonemia must be excluded as fast as possible. Any delay in recognition and start of treatment of hyperammonemia may have deleterious consequences for the patient. Treatment largely depends on the underlying cause but is, at least in pediatric patients, mainly aimed at establishing anabolism to avoid endogenous protein breakdown and amino acid imbalances. In addition, pharmacological treatment options exist to improve urea cycle function or to remove nitrogen, but their use depend on the underlying disorder. To improve the prognosis of acute hyperammonemia, an increased awareness of this condition is probably more needed than anything else. Likewise, the immediate start of appropriate therapy is of utmost importance. This review focuses on a better understanding of factors leading to ammonia elevations and on practical aspects related to diagnosis and treatment in order to improve clinical management of hyperammonemia.

Urea-splitting urinary tract infection contributing to hyperammonemic encephalopathy

BACKGROUND

We present a case of severe neurological symptoms caused by hyperammonemia, secondary to a urinary tract infection with urea-splitting bacteria.

INVESTIGATIONS

Blood analysis, urinalysis, urine culture, abdominal ultrasonography, cystography, CT.

DIAGNOSIS

Hyperammonemia as a result of urinary tract infection with urea-spliting bacteria.

MANAGEMENT

Desobstruction of the urinary tract and bladder or pouch rinsing, antibiotics, reduction of the dietary and endogenous nitrogen load, and endogenous nitrogen breakdown. Identification, prevention and treatment of underlying causes.

Hyperammonemic encephalopathy induced by a combination of valproate and pivmecillinam

We describe the clinical and neurophysiological findings in a case of hyperammonemic encephalopathy. A 72-year-old woman taking valproate (VPA), as monotherapy for her partial epilepsy developed urinary tract infection. She was treated with pivmecillinam 600 mg daily. The following days she deteriorated and became stuporous. At admission her serum ammonia level was increased (113 mmol/l) but the liver function appeared normal. EEG showed bilateral triphasic waves and continuous high-amplitude delta-theta wave. The patient recovered rapidly after discontinuation of VPA and i.v. treatment with cefuroxime for her urinary tract infection. VPA-induced hyperammonemic encephalopathy in adults is a rare phenomenon, especially when VPA is used as monotherapy. It has been suggested that the VPA-induced hyperammonemic encephalopathy is due to reduced serum carnitine concentration. Pivmecillinam, a widely used antibiotic for treatment of urinary tract infections, is also known to decrease the serum carnitine concentration. Our case shows that caution is required when treatment with VPA is combined with pivmecillinam due to the risk of developing hyperammonemic encephalopathy.

Short report: Hyperammonaemia in critically ill septic infants

Three infants with subphrenic abscess, pyonephrosis, and obstructive ureterocoele respectively had grossly increased concentrations of plasma ammonia. This was considered to be a result of infections with urea splitting organisms. All died in spite of intensive care support, including specific measures to reduce plasma ammonia.

Hyperammonemic coma caused by Providencia rettgeri infection in a child with prune belly syndrome

OBJECTIVE: To report a case of hyperammonemic encephalopathy in the absence of liver disease caused by a urinary tract infection with a previously unreported organism. DESIGN: Case report. SETTING: Pediatric intensive care unit. Patient: Critically ill child who presented with hyperammonemic coma. INTERVENTION: Bladder drainage and antimicrobial therapy for the urinary tract infection. Measurements: Rapid resolution of the hyperammonemia. MAIN RESULTS: Rapid improvement in the patient's neurologic status and a return to his baseline function without neurologic deficit. CONCLUSIONS: Patients with abnormal urinary collecting systems who present with altered mental status should have a serum ammonia concentration sent as part of the initial evaluation. We have added Providencia species to the list of documented causative organisms in this rare association between urinary tract infections and hyperammonemia.

Awakenings to the pathogenicity of urease and the requirement for continuous long term therapy

Urease is an enzyme found in plants and bacteria, but not mammals. It catalyzes the conversion of urea to carbon dioxide and ammonia. Ammonia shortens the life span of cells; and higher concentrations cause tissue necrosis and cytolysis. Twenty percent of total body urea is converted to ammonia by bacterial urease in the colon. Small injections of urease immunize animals by producing antiurease, a gamma globulin, which inactivates urease. Immunization eliminates the colonic conversion of urea to ammonia. Injection of urease produces ammonia intoxication making immunization hazardous. Although previously impossible, a non enzymatic urease antigen was synthesized by covalently bonding jack bean urease with glutaraldehyde. This antigen stimulated the production of antiurease that inactivates native urease. Helicobacter pylori, a potent urease producer, has been implicated in peptic ulcer, gastritis and other inflammatory bowel lesions. The pathogenicity of H pylori is dependent on its urease production. Immunization to urease can render H pylori non pathogenic. Cirrhotics develop encephalopathy and hyperammonemia because their livers fail to convert all the ammonia in portal venous blood to urea and collaterals develop by passing the liver. Colonic ammonia increases the turnover rate of colonic mucosa. Ammonia absorbed into the portal venous system is transported to the liver where it is reconverted to urea. Absorbed ammonia adversely influences liver function. Infections with urease producing organisms destroy the renal parenchyma and produce struvite stones. Urease immunization aids colonic healing and prevents uremic colitis. Absorbed ammonia is a noxious influence on the liver. Animals immunized to urease regenerate the liver faster and are less susceptible to hepatotoxins. Immunization to urease ameliorates cirrhosis. Proteus and other urease producers become non toxic and do not damage the renal parenchyma. Urease is responsible for the pathogenicity of infections with urease producing organisms. Immunization to urease renders urease producing organisms non pathogenic.

Ammonia levels in paediatric ureterosigmoidostomy patients: a screen for hyperammonaemia?

Hyperammonaemia in the urological patient is a rare and potentially grave condition. It has been reported most frequently in association with ureterosigmoidostomy, where clinical neurological symptoms have developed abruptly in association with markedly elevated plasma ammonia levels. The purpose of this study was to determine whether ureterosigmoidostomy patients might have subclinically elevated plasma ammonia levels, which would put them at risk of subsequently developing hyperammonaemic encephalopathy. Both urine and plasma ammonia levels were assayed in 10 asymptomatic paediatric urological patients with ureterosigmoidostomy. Ten paediatric colocystoplasty patients served as controls. Urine pH and urine ammonia levels were significantly higher in the ureterosigmoidostomy group. There was no significant difference in plasma ammonia levels between ureterosigmoidostomy and colocystoplasty patients. In none of the patients was the plasma ammonia level elevated, but 1 ureterosigmoidostomy patient had an exceedingly high urine ammonia level. It was concluded that an annual serum ammonia level in an asymptomatic ureterosigmoidostomy patient is probably not a valuable screen for subclinical hyperammonaemia.

Construction of a urease-negative mutant of Proteus mirabilis: analysis of virulence in a mouse model of ascending urinary tract infection

Proteus mirabilis, a urease-producing uropathogen, causes serious urinary tract infections in humans. To specifically evaluate the contribution of urease to virulence, a mutation was introduced into P. mirabilis HI4320 by homologous recombination. Virulence was assessed in the CBA mouse model of ascending urinary tract infection. Twenty mice each were challenged transurethrally with P. mirabilis HI4320 and its urease-negative derivative (1 x 10(9) to 2 x 10(9) CFU). At 48 h animals were sacrificed and the mean log10 CFU per milliliter of urine (parent, 6.23; mutant, 4.19; P = 0.0014) or per gram of bladder (parent, 6.29; mutant, 4.28; P = 0.0002), left kidney (parent, 4.11; mutant, 1.02; P = 0.00009), and right kidney (parent, 4.11; mutant, 2.43; P = 0.036) were all shown to be significantly different. These data demonstrate a role for urease as a critical virulence determinant for uropathogenic P. mirabilis.

Hyperammonemic encephalopathy: a complication associated with the prune belly syndrome

Hyperammonemic encephalopathy in the urological patient is a rare but grave condition. In the pediatric urological population it has been associated with massively dilated upper tracts and urinary infection with urea-splitting organisms. We report 2 cases of hyperammonemic encephalopathy in association with the prune belly syndrome. Both patients presented comatose with markedly elevated serum ammonia levels and Proteus mirabilis urinary tract infection. Intravenous antibiotics and catheter drainage resulted in dramatic reversal of the encephalopathy. The pathophysiology of hyperammonemic encephalopathy in association with the prune belly syndrome and a review of the literature are presented.

The ecology and pathogenicity of urease-producing bacteria in the urinary tract

Urease activity is a physiological function of many bacteria that enables these organisms to utilize urea as a source of nitrogen. The association of ureolytic bacteria with human or animal hosts varies widely from a commensal relationship as demonstrated with skin microflora, a symbiotic relationship in the gastrointestinal tract, to a pathogenic relationship in the urinary tract. Since similar or identical species of bacteria such as Staphylococcus aureus are found in all three environments, the effect of urease activity on the host must be solely a function of the environment of these organisms. In this review, the importance of urease to bacteria is discussed, identifying the gastrointestinal tract as a major reservoir of ureolytic bacteria and investigating the urinary tract environment and the infectious struvite stone production that often accompanies urease-producing bacteria there. Finally, an infection model is presented which explains the development and growth of these urinary calculi and their remarkable persistence in spite of modern urological treatments.