Medullary cystic disease is a disorder involving the formation of cysts in the kidney medulla. The condition is inherited in most cases. The disorder causes an inability to concentrate the urine.

This results in excessive fluid loss from the body, which is accompanied by loss of sodium. This is a "high output" type of chronic renal failure (renal failure with increased urine volume, but with all other aspects of decreased kidney function).

The disorder is rare. This disorder causes end-stage renal disease in less than 5% of the pediatric end-stage renal disease population. The disorder runs in families, and the inheritance patterns vary.

There is X-linked and autosomal dominant inheritance in different families. X-linked inheritance is carried on the X chromosome, and is expressed in males that inherit the faulty gene from their mother. It is expressed in females that inherit the faulty gene from both parents. Females that only inherit the gene from one parent will not develop the disorder, but can pass it on to their children. With autosomal dominance, if one parent has the gene for the disorder, 50% of the children will display symptoms.

Risk factors include an individual or family history of medullary cystic disease, chronic renal failure, or increased urinary volume with excessive thirst.

• High urine output, unrelated to fluid intake
• Urine pale colored
• Nocturia (need to urinate at night)
• Pale skin
• Weakness
• Weight loss
• Nausea, vomiting
• General ill feeling
• Fatigue
• Headache
• Frequent hiccups
• Generalized itching (pruritus)
• Easy bruising or bleeding (such as vomiting blood or blood in the stool)
• Decreased alertness
  • Drowsiness, somnolence, lethargy
  • Confusion, delirium
  • Coma
• Muscle twitching or muscle cramps
• Seizures
• Increased skin pigmentation (skin may appear yellow or brown)
• Decreased sensation in the hands, feet, or other areas

• High urine sodium
• Progressively increasing creatinine levels
• Progressively increasing BUN
• Progressively decreasing creatinine clearance
• Possibly increasing urine potassium
• Arterial blood gases and blood chemistry showing metabolic acidosis
• IVP showing small kidneys
• Abdominal ultrasound or abdominal CT scan showing small kidneys or multiple cysts on the kidneys
• Renal biopsy showing interstitial nephritis or medullary cystic kidney

Treatments focus on controlling symptoms, minimizing complications, and slowing the progression of the disease.

Adequate fluid intake should be encouraged. Dietary restrictions may slow the build-up of wastes in the bloodstream and control associated symptoms such as nausea and vomiting. The diet is often low protein, with high levels of carbohydrates to make up calories.

Potassium, phosphorus, and other substances may be restricted. Salt should rarely be restricted in people with medullary cystic disease, even if hypertension or fluid retention is present.

Loss of sodium from the kidney can cause severe sodium depletion in the body. After evaluation of daily requirements, extra salt may be advised.

Medications, such as iron and erythropoietin, may be needed to control anemia. Blood transfusions are needed very rarely.

Associated diseases that cause or result from chronic renal failure must be controlled. Hypertension, congestive heart failure, chronicurinary tract infection, kidney stones, obstructions of the urinary tract (chronic urethral obstruction), glomerulonephritis, and other disorders should be treated as appropriate.

Dialysis or kidney transplantation may eventually be required.

• Hyponatremia
• End-stage renal disease
• Pericarditis, cardiac tamponade
• Platelet dysfunction
• Gastrointestinal bleeding, ulcers
• Hemorrhage
• Anemia
• Peripheral neuropathy
• Weakening of the bones, fractures, joint disorders
• Permanent skin pigmentation changes
• Itching
• Changes in glucose metabolism
• Changes in electrolyte levels, electrolyte abnormalities including hyperkalemia
• Miscarriage, menstrual irregularities, infertility
• Congestive heart failure
• Hypertension