Renal agenesis: Most people are born with two kidneys. But one in 4,000 infants (more boys than girls) come into the world with only one organ, the characteristic signal of renal agenesis. It is frequently identified because of pregnancy screening, often to evaluate another problem. On occasion, imaging tests will pick up a very small kidney, located in an abnormal position. Your physician may recommend another special imaging test on your infant to determine whether there is a small amount of kidney tissue missed by the initial study.
Renal dysplasia: An abnormal tissue development that can be confined to a small portion of one (unilateral) or both (bilateral) kidneys, arranged in a specific pattern within the kidney or randomly present throughout one or both kidneys.
Renal hypoplasia: Small kidneys which are otherwise normal. This condition may involve one or both sides. Renal hypoplasia does not appear to be an inherited condition, nor does it occur, more often in boys than girls. In fact, while the true incidence is unknown, it has been reported in as high as 2.5 percent of the population. The size of the kidney determines potential problems in the future. If a child’s kidneys are extremely small, their function may decrease as the child enters his/her teens. Although a rarity, kidney failure may occur which would require supportive measures.
Renal hypoplasia may also be associated with abnormalities of the ureter, the tube that connects the kidney to the bladder. This condition is marked by either a backflow of urine from the bladder into the kidney or an obstruction of the ureter at the juncture where it normally enters the kidney.
Autosomal recessive polycystic kidney disease (ARPK): Most commonly noted in infants, ARPK also has been described as “infantile polycystic kidney disease.” It occurs in one in 5,000 to one in 40,000 births, even though the condition may also first appear during adolescence or young adulthood. There is a spectrum of severity with this disease, appearing at an early age, progressing to variable degrees of kidney failure. ARPK is also linked to fibrosis, an abnormal overgrowth of connective tissue, in the liver.
ARPK in a fetus is often identified during a fetal sonogram at the time of pregnancy. The urologist bases a diagnosis on kidneys that are misshaped and considerably larger than normal. At birth, you can expect symptoms such as abdominal lumps on both sides and/or kidney failure. While kidneys vary in size, the characteristic cysts of this disorder are very small and are spread randomly throughout the kidneys.
Autosomal dominant polycystic kidney disease (ADPK): ADPK is one of the most common causes of kidney failure, present in 10 percent of patients on hemodialysis. The incidence rate is one in 500 to one in 1,000, with approximately 500,000 Americans suffering from a condition that results in an enlarged cyst-filled kidney. Most patients are diagnosed between ages 30 and 50 but the disease, previously identified as “adult polycystic kidney disease,” can appear in all age groups. Fifty percent of children born to individuals with this disease will also inherit it.
In terms of symptoms, infants usually experience serious kidney failure and respiratory problems. Children older than age one have high blood pressure or enlarged kidneys. If you are an adult, you may experience visible or microscopic blood (hematuria) in your urine, along with flank pain, high blood pressure or occasional gastrointestinal symptoms, due to enlarged kidneys or associated colonic diverticula. Both kidneys will have varying-sized cysts, which may also appear in the liver. Approximately 10 to 40 percent of individuals also experience an abnormality of the blood vessels in the brain, which can lead to sudden bleeding and risk of aneurysm. While ADPK can be debilitating, the good news is that the risk of a kidney tumor is no greater with this disease than the risk in the general population.
Juvenile nephronophthisis and medullary cystic disease complex: Occurring in one in 50,000 to one in 100,000 births, juvenile nephronophthisis is found in 10 to 20 percent of children with kidney failure. Sufferers of this rare condition complain of great thirst and urinate excessively. They may also have eye problems, skeletal abnormalities and liver fibrosis. Less than half of those diagnosed as children have cysts on their kidneys. Kidney failure usually occurs in the early teens as part of juvenile nephronophthisis. With medullary cystic disease, kidney failure usually occurs in adults between the ages of 20 and 40. Symptoms of the latter condition include cysts of varying size, usually less than one centimeter.
Renal cystic disease syndromes: Renal cystic disease is common in individuals with a variety of other serious maladies. For instance:
Tuberous sclerosis (TS): Consisting of three characteristic components — epilepsy, mental retardation and fleshy nodules beneath the skin — tuberous sclerosis occurs in one in 9,000 to one in 70,000 newborns. Renal cysts develop in 20 percent of individuals, most often in childhood. The incidence of kidney tumors is greater in patients with tuberous sclerosis than in the normal population.
von Hippel-Lindau disease: An inherited condition that occurs in 50 percent of children with an affected parent. Manifested by blood vessel abnormalities of the brain and eye, this disease also produces cysts of the pancreas, kidney and epididymis. With this condition, benign fatty tumors are interspersed between the cysts. Tumors of the adrenal gland (pheochromocytoma) are also present. While renal cysts occur in approximately 80 percent of patients with von Hippel-Lindau disease, kidney cancer is present in just under 40 percent of individuals. The cysts and tumors usually do not produce symptoms unless they become very large, triggering pain or bleeding due to ruptures.
Multicystic dysplastic kidney (MCDK): The most common type of pediatric renal cystic disease, MCDK is also the most common abdominal mass, which can be felt as a lump in an infant. MCDK is often identified during a fetal sonogram at the time of pregnancy. On sonography, the kidney appears like a bunch of grapes with very little kidney tissue, rather than an organ with normal contours. The kidney usually has no function. In 10 percent of sufferers, an obstruction at the ureteropelvic junction may occur in the opposite organ; in 20 percent of cases, there is also abnormal urine backflow from the bladder into the ureter. When MCDK occurs on both sides, the result is a spontaneous abortion of the fetus. High blood pressure and renal tumors may be associated with this condition in children, but are exceedingly rare.
Simple renal cyst: Simple renal cysts occur in approximately one in 500 individuals between birth and age 18, appearing similarly in both genders. (Autopsy reports have shown the incidence to be approximately 50 percent at age 50.) Most simple cysts do not cause problems but are usually found when an individual is undergoing tests for other problems. Large renal cysts may produce abdominal pain, blood in the urine (hematuria) or, in rare incidents, high blood pressure. Simple renal cysts are not associated with kidney cancer. But the risk of malignancy increases if the cyst is identified as complex (with multiple chambers or irregularities in the wall) and/or contains calcium.
Medullary sponge kidney: Characterized by multiple, small cysts in the tubules that collect urine, medullary sponge kidney is estimated to be present in one of 5,000 to one of 20,000 individuals. Patients may exhibit kidney pain, blood in the urine and/or higher calcium output in their urine.
Acquired renal cystic disease: Acquired renal cystic disease occurs in individuals who have long-standing renal failure, particularly those undergoing dialysis. The risk of kidney cancer is significantly increased with this disease. Patients usually complain of back pain or blood in the urine.