Medullary cystic disease is a hereditary kidney disorder characterized by gradual and progressive loss of kidney function because of cysts in the kidney medulla (center).
Alternative Names
Familial juvenile nephrophthisis; Senior-Loken syndrome
Causes, incidence, and risk factors
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 .
Signs and tests
The blood pressure may be high, with mild to severe hypertension . A neurologic examination may show damage to multiple nerves. Abnormal heart or lung sounds may be heard through a stethoscope. A CBC may show significant anemia (decreased red blood cells). A urinalysis shows dilute urine, excretion of small amounts of urine protein , or other abnormalities. (An abnormal urinalysis may occur 6 months to 10 or more years before symptoms appear.) These tests also help confirm the diagnosis:
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 A renal or abdominal X-ray , abdominal CT scan, abdominal MRI , or abdominal ultrasound may reveal changes indicating chronic renal failure . Both kidneys are usually smaller in size than normal.
Treatment
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 , chronic urinary 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.
Expectations (prognosis)
There is no cure for chronic renal failure resulting from medullary cystic disease. Untreated, it usually progresses to end-stage renal disease . Chronic , lifelong treatment may control the symptoms of chronic renal failure.
Complications
HyponatremiaEnd-stage renal diseasePericarditis , cardiac tamponade
Platelet dysfunction Gastrointestinal bleeding, ulcers
Hemorrhage AnemiaPeripheral 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 failureHypertension
Prevention
This is an inherited disorder, but the way it is inherited varies. Prevention may not be possible.