Definition of Medullary cystic kidney disease:

Medullary cystic kidney disease (MCKD) is a hereditary disorder in which cysts in the center of each kidney cause the kidneys to gradually lose their ability to work.

Causes, incidence, and risk factors:

Medullary cystic kidney disease (MCKD) is very similar to the childhood disease familial juvenile nephronophthisis (NPH). Both lead to scarring of the kidney and formation of fluid-filled cavities (cysts) in the deeper parts of the kidney.

In these conditions, the kidneys don't concentrate the urine enough, leading to excessive urine production and loss of sodium.

MCKD occurs in older patients and is inherited in an autosomal dominant pattern. NPH occurs in young children and is usually due to autosomal recessive inheritance.

NPH may be associated with non-kidney features (like eye problems), while MCKD is limited to the kidneys.

Symptoms:

Early in the disease, symptoms may include:

• Excessive urination (polyuria)
• Low blood pressure
• Need to urinate at night (nocturia)
• Salt cravings
• Weakness

Late in the disease, symptoms of kidney failure may develop, which include:

• Coma
• Confusion
• Decreased alertness
• Delirium
• Drowsiness
• Easy bruising or bleeding
• Extreme sleepiness (lethargy)
• Fatigue
• Frequent hiccups
• General ill feeling
• Generalized itching
• Headache
• Increased skin pigmentation (skin may appear yellow or brown)
• Muscle twitching or muscle cramps
• Nausea
• Pale skin
• Reduced sensation in the hands, feet, or other areas
• Seizures
• Unintentional weight loss
• Vomiting blood or blood in the stool
• Weakness

Signs and tests:

Laboratory tests that may be done include:

• 24-hour urine volume
• Blood pressure measurement (may be low)
• BUN (blood urea nitrogen)
• Complete blood count
• Creatinine level and creatinine clearance
• Urine specific gravity (will be low)

The following tests can help diagnose this condition:

• Abdominal ultrasound or abdominal CT scan
• Renal biopsy

Treatment:

There is no cure for this disease. At first, treatment focuses on controlling symptoms, reducing complications, and slowing the progression of the disease. Because of the loss of water and salt, the patient will need to drink plenty of fluids and take salt supplements to avoid dehydration.

As the disease gets worse, kidney failure develops. Treatment may involve medications and diet changes to limit foods containing phosphorus and potassium. Dialysis and a kidney transplant may be needed. For detailed information on treatment, see the articles on chronic kidney failure and end-stage kidney disease.

Expectations (prognosis):

Most persons with MCKD reach end-stage kidney disease between the ages of 30 and 50. Lifelong treatment may control the symptoms of chronic kidney failure.

Complications:

• Anemia
• Cardiac tamponade
• Changes in glucose metabolism
• Changes in electrolyte levels ( hyperkalemia)
• Congestive heart failure
• End-stage kidney disease
• Gastrointestinal bleeding, ulcers
• Hemorrhage
• High blood pressure
• Hyponatremia
• Infertility
• Menstrual irregularities
• Miscarriage
• Pericarditis
• Peripheral neuropathy
• Permanent skin coloring changes
• Platelet dysfunction
• Weakening of the bones, fractures, joint disorders

Calling your health care provider:

Call for an appointment with your health care provider if you have any symptoms of medullary cystic disease.

Prevention:

This is an inherited disorder, but the way it is inherited varies. Prevention may not be possible.