The Bartter syndrome

A 12-month-old girl whose height and weight are less than the fifth percentile; she has had several bouts of constipation and two previous admissions for dehydration. She is again admitted for dehydration and is noted to have serum potassium of 2.7 mEq/L.

  1. Nephrotic syndrome
  2. Henoch-Schönlein purpura nephritis
  3. Bartter syndrome
  4. Acute glomerulonephritis
  5. Idiopathic hypercalciuria

Explanation

Idiopathic hypercalciuria causes recurrent gross hematuria, persistent microscopic hematuria, and complaints of dysuria or abdominal pain without initial stone formation. Over time, however, stones may form in 15% of cases.

With acute glomerulonephritis, oliguria (often presenting with dark, cola-colored urine) frequently occurs as a direct consequence of the disease process itself; on occasion, it can be profound, with virtual anuria for several days. During this period of time, it is vital to monitor and restrict fluid intake lest massive edema, hypervolemia, and even pulmonary edema and death occur.

Elevated levels of cholesterol and triglycerides are common in nephrotic syndrome because of increased generalized protein synthesis in the liver (including lipoproteins) and because of a decrease in lipid metabolism due to reduced plasma lipoprotein lipase levels. In the nephrotic syndrome, albumin is lost in the urine and, despite increased hepatic synthesis, serum levels drop. The upper limit of protein excretion in healthy children is 0.15 g/24 h; in nephrotic syndrome, proteinuria can exceed 2.0 g/24 h. When the serum protein level drops low enough, the oncotic pressure of the plasma becomes too low to balance the hydrostatic pressure. Plasma volume, therefore, decreases as edema occurs. Periorbital edema in the morning and scrotal edema in boys during the day is commonly reported. Endocrine and renal mechanisms then partially compensate by retaining water and salt. Overzealous monitoring and restriction of water and salt intake are usually not required.

Hypertension commonly accompanies glomerulonephritis, but only occasionally accompanies nephrotic syndrome. Diuretics are sometimes used in both nephrotic syndrome and glomerulonephritis with temporary effect, but are not curative. A combination of albumin infusions followed by a diuretic also has been used to temporarily decrease the edema in patients with nephrotic syndrome. Because both illnesses are usually self-limited, temporary measures are important. In all cases, blood pressure must be evaluated for the age of the child (eg, the 6-year-old girl with a blood pressure of 120/80 mm Hg is significantly hypertensive).

Bartter syndrome (also known as juxtaglomerular hyperplasia) is an autosomal recessive condition that causes hypokalemia, hypercalciuria, alkalosis, hyperaldosteronism, and hyperreninemia; blood pressure is usually normal. Clinical presentations occurring frequently between 6 and 12 months of age include failure to thrive with constipation, weakness, vomiting, polyuria, and polydipsia. Treatment is aimed at preventing dehydration, providing nutritional support, and returning the potassium level to normal.

Henoch-Schönlein purpura nephritis presents with a purpuric rash, arthritis, and abdominal pain, and has an associated glomerulonephritis that can cause gross or microscopic hematuria. IgA (Berger) nephropathy is the most common chronic glomerulonephritis. Initially thought to be benign, it is now known to progress over decades to chronic renal failure in many afflicted patients. IgA is found in the mesangium, but this occurs with other disease processes as well. The most common clinical finding is hematuria; episodic gross hematuria is frequently associated with a febrile illness.