medullary sponge kidney

Medullary Sponge Kidney 

Definition

Medullary sponge kidney is a congenital defect of the kidneys where the kidneys fill with pools of urine.

Description

One of every 100 to 200 people have some form of this disease. The kidneys filter urine from the blood and direct it down tiny collecting tubes toward the ureters (ducts that carry urine from the kidney to the bladder). These tiny tubes gradually join together until they reach the renal pelvis, where the ureters begin. As the tubes join, they are supposed to get progressively bigger as they get fewer in number. In medullary sponge kidney, the tubes are irregular in diameter, forming pools of urine along the way. These pools encourage stone formation and infection.

Causes and symptoms

Although some cases of this disorder seem to be inherited, usually the cause is not known.

The symptoms associated with medullary sponge kidney are those related to infection and stone passage. Infection causes fever; back and flank pain; cloudy, frequent, and burning urine; and general discomfort. Stones cause pain in the flank or groin as they pass. They usually cause some bleeding. The bleeding may not be visible in the urine, but it is apparent under a microscope.

Diagnosis

Recurring kidney infections, bleeding, or stones will prompt x rays of the kidneys. The appearance of medullary sponge kidney on an intravenous pyelogram (x rays of the upper urinary system) is characteristic.

Treatment

Many people never have trouble with this disorder. For those that do, infections and stones will need periodic treatment. Infections should be treated with antibiotics early in order to prevent kidney damage. Stones may need to be surgically removed. Often, removal can be accomplished without an incision but rather by reaching up with instruments through the lower urinary tract to grab the stones. There is also a new method of stone treatment called shock wave lithotripsy. A special machine delivers a focused blast of shock waves that breaks stones into sand so that they will pass out naturally. It is considered reasonably safe and usually effective.

Prognosis

Ignoring symptoms can result in progressive damage to the kidneys and ultimate kidney failure, but attentive early treatment will preserve kidney function.

Prevention

Diligent monitoring for infection at regular intervals and at the first symptom will give the best long-term results. By drinking extra liquids, most stones can be prevented. The most common kind of stones, calcium stones, can be deterred by regularly taking a medication that encourages urine production (thiazide diuretic).

Resources

Organizations

American Association of Kidney Patients. 100 S. Ashley Dr., #280, Tampa, FL 33602. (800) 749-2257. http://www.aakp.org.

American Kidney Foundation. 6110 Executive Boulevard, #1010, Rockville, M D 20852. 800-638-8299.

National Kidney Foundation. 30 East 33rd St., New York, NY 10016. (800) 622-9010. http://www.kidney.org.

Key terms

Congenital — Present at birth.

Intravenous pyelogram — X rays of the upper urinary system using a contrast agent that is excreted by the kidneys into the urine.

Thiazide diuretic — A particular class of medication that encourages urine production.

---

kidney /kid·ney/ (kid´ne) either of the two organs in the lumbar region that filter the blood, excreting the end-products of body metabolism in the form of urine, and regulating the concentrations of hydrogen, sodium, potassium, phosphate, and other ions in the extracellular fluid.

---

abdominal kidney  an ectopic kidney just above the iliac crest.

amyloid kidney  one with renal amyloidosis.

artificial kidney  an extracorporeal device through which blood may be circulated for removal of elements that normally are excreted in the urine; a hemodialyzer.

cake kidney  a solid, irregularly lobed organ of bizarre shape, formed by fusion of the two renal anlagen.

cicatricial kidney  a shriveled, irregular, and scarred kidney due to suppurative pyelonephritis.

fatty kidney  one with fatty degeneration.

flea-bitten kidney  one with scattered petechiae on its surface.

floating kidney  nephroptosis.

fused kidney  a single anomalous organ developed as a result of fusion of the renal anlagen.

head kidney  pronephros.

horseshoe kidney  an anomaly in which the right and left kidneys are linked at one end by tissue.

hypermobile kidney  nephroptosis.

lumbar kidney  an ectopic kidney found opposite the sacral promontory in the iliac fossa, anterior to the iliac vessels.

lump kidney  cake k.

medullary sponge kidney  a usually asymptomatic, congenital condition in which small cystic dilatations of the collecting tubules of the renal medulla give the kidney a spongy feeling and appearance.

middle kidney  mesonephros.

pelvic kidney  an ectopic kidney found opposite the sacrum and below the aortic bifurcation.

polycystic kidneys  see polycystic kidney disease, under disease.

primordial kidney  pronephros.

sigmoid kidney  an anomaly in which the two kidneys are fused in the form of a capital Greek letter sigma.

sponge kidney  medullary sponge k.

thoracic kidney  an ectopic kidney that protrudes above the diaphragm into the posterior mediastinum.

waxy kidney  amyloid k.

---

medullary sponge kidney

n.

A cystic disease of the renal pyramids characterized by calculus formation and hematuria but usually not with renal failure.

---

medullary sponge kidney,

a congenital defect of the kidney leading to cystic dilation of the collecting tubules. People with this defect often develop a kidney stone or an infection of the kidney caused by urinary stasis. The condition is diagnosed by urographic techniques. Treatment includes drugs to acidify the urine and a diet low in calcium and high in fluids to discourage formation of stones.

---

medullary sponge kidney

Polycystic kidneys, see there