Food safety

Melamine


Epidemiology and treatment

Suggested surveillance case definition

Identification of possible cases related to the consumption of melamine-contaminated products from China

Member States should be aware of the possible distribution of the contaminated products either through formal or informal channels, because of the large quantities involved and the seriousness of the public health consequences of this event. The period of production of contaminated product is uncertain and the incriminated raw material and products may have been exported as infant formula or other milk containing products to other Member States. Therefore WHO is suggesting this surveillance case definition to Member States to increase their awareness of signs that their population may be affected.

Clinical description

The following symptoms have been observed in infants affected by the melamine-contaminated infant formula in China:

  • Unexplained crying in infants, especially when urinating, possible vomiting
  • Macroscopic or microscopic haematuria
  • Acute obstructive renal failure: oliguria or anuria
  • Stones discharged while passing urine. For example, a baby boy with urethral obstruction with stones normally has dysuria
  • High blood pressure, edema, painful when knocked on kidney area

WHO experts believe an additional symptom may be unexplained fever arising from urinary tract infections/bacteraemia secondary to urine stasis resulting from obstruction.

Surveillance case definition

A case is defined as an infant with kidney stones or other kidney problems (e.g. anuria, renal failure) having consumed powdered infant formula produced in China before 6 August 2008, and where other potential causes of kidney stones have been excluded by differential diagnosis.

Treatment

The World Health Organization has agreed to circulate the information contained herein regarding the treatment plan that is being implemented in China by the Ministry of Health. The information below does not reflect the rules, regulations, policies and guidelines of the World Health Organization.

The following regimen has been issued by the Ministry of Health, China.

Clinical manifestations
  • Unexplained crying, especially when urinating, possible vomiting
  • Macroscopic or microscopic haematuria
  • Acute obstructive renal failure: oliguria or anuria
  • Stones discharged while passing urine. For example, a baby boy with urethral obstruction with stones normally has dysuria
  • High blood pressure, edema, painful when knocked on kidney area
Key diagnostic criteria
  • Been fed with melamine-contaminated infant milk formula
  • Having one or more of the above clinical manifestations
  • Laboratory test results: routine urine tests with macroscopic or microscopic haematuria; blood biochemistry; liver and kidney function tests; urine calcium/creatinine ratio (usually normal); urinary red blood cell morphology shows normal morphology of red blood cells (not glomerular haematuria); parathyroid hormone test (usually normal).
  • Imaging examination: preferably ultrasound B exam of urinary system. If necessary, abdominal CT scan and intravenous urography (not to be used in case of anuria or renal failure). Kidney radionuclide scans can be used where available to evaluate renal function.
  • Ultrasound examination features:
    • General features: bilateral renal enlargement; increased echo on solid tissue; normal parenchyma thickness; slight pyelectasia and calicectasis; blunt renal calyx. If the obstruction locates in the ureter, then the ureter above the obstruction point dilates. Some cases have edema with perinephric fat and soft tissue around the ureter. As the disease develops, the renal pelvis and ureter wall may have secondary edema. A few cases have ascites.
    • Stone features: most stones affect the collecting system and ureters on both sides. Ureteral stones are mostly at pelviureteral junction, the part where the ureter passes across iliac artery, and ureter-bladder junction. Stones stay collectively, covering massive areas. Lighter echo in the background. Most stones are different from the calcium oxalate stones. Urinary tract is mostly completely obstructed by the stones.
Differential diagnosis
  • Haematuria differentiation: need to rule out glomerular haematuria.
  • Stone differentiation: the stones are normally radiolucent and have a negative image on urinary tract x-ray. This feature differentiates the stones from those of radiopaque stones of calcium oxalate and calcium phosphate.
  • Differentiation of acute renal failure: need to rule out pre-renal and renal failure.
Clinical treatment
  • Immediately stop using melamine-contaminated infant formula milk powder.
  • Medical treatment: use infusion and urine alkalinization to dispel the stones. Correct the water, electrolyte and acid-base imbalance. Closely monitor routine urine tests, blood biochemistry, renal functions, ultrasound findings (with particular attention to the renal pelvis, ureter expansion, and the change of the stones in shape and location). If the stones are loose and sand-like, they are very likely to be passed out with urine.
  • Treatment of complicated acute renal failure: priority should be given to the treatment of life-threatening complications such as hyperkalemia. Measures include the administration of sodium bicarbonate and insulin. If possible, blood dialysis and peritoneal dialysis can be used early. Surgical measures can be taken to remove the obstruction if necessary.
  • Surgical treatment: if medical treatment is not effective, and hydrocele and kidney damage present, or blood dialysis and peritoneal dialysis are not available in case of renal failure, surgical methods can be considered to remove the obstruction. Stones can be removed by different methods including cystoscope retrograde intubation into the ureter, percutaneous kidney drainage, surgical removal and percutaneous kidney stone removal. Extracorporeal shock wave lithotripter (ESWL) is greatly limited in its application, because the stones are loose and mainly composed of urate, and the patients are infants.
Follow-up

Once the urinary obstruction is relieved, and the general condition and renal function and urination are back to normal, the children can be discharged.

Key issues to follow-up

Urine routine tests; ultrasound of urinary system; renal function tests; IVP (intravenous pyelogram) if necessary.

Share