Patients suffering from long term kidney disease or severe hypertension eventually end up with smaller kidneys because tissue is lost to scarring. For this reason, enlarged kidneys are a relatively rare phenomenon and only associated with a few special diseases. Enlarged kidneys occur because of birth defects, inflammation or the presence of abnormal tissue such as a cancer or a cyst.
Polycystic Kidney Disease
Patients with polycystic kidney disease have enlarged kidneys because their kidneys have become riddled with cysts. One variant of this disease occurs because of a dominant gene and another from a recessive gene. Symptoms in patients with the recessive variant can become so severe that they are obvious at birth. Symptoms caused by the dominant variant can prove very mild and not begin until early or middle adulthood.
According to the Merck Manual, "more than half of the people who have this disease develop kidney failure at some time in their life." If kidney failure occurs, dialysis or transplant will prevent death.
Hydronephrosis
Hydronephrosis involves distension and dilation of the kidneys and related structures. This means the kidneys have become swollen. This is usually caused by an obstruction that prevents urine from flowing freely. According to the Merck Manual, "an enlarged kidney may be palpable on examination." Reflux, or back flow of urine into the kidney can occur.
Hydronephrosis can occurs because of a birth defect, cancer, kidney stones and other conditions. If related to a birth defect, physicians often diagnose when the baby is in utero.
Treatment varies depending upon the cause. Doctors often perform surgery if this results from cancer or birth defects.
Pyelonephritis
Pyelonephritis is the medical name for inflammation of the kidneys caused by infection. Since the kidneys are part of the urinary tract, pyelonephritis is classified as a urinary tract infection or UTI. According to the Merck Manual, "one or both kidneys may be enlarged and painful."
Symptoms of pyelonephritis often come on suddenly. Patients suffer from chills, fever, nausea and lower back pain. They often have symptoms of cystitis or bladder infection as well such as painful, frequent peeing.
