| disease | Adult Polycystic Kidney Disease |
Adult polycystic kidney disease is an autosomal dominant inherited disorder, almost always bilateral (accounting for 95% of total cases). Although cases of infants with adult polycystic kidney disease have been reported in the literature, the condition differs in infants compared to adults. Infantile polycystic kidney disease is an autosomal recessive inherited disorder with a short survival period, whereas adult polycystic kidney disease typically does not present symptoms before the age of 40. Multiple cysts of similar morphology can also be observed in the liver, spleen, and pancreas. The kidneys in polycystic kidney disease are larger than normal, with their surfaces covered in cysts of varying sizes.
bubble_chart Etiology
Existing evidence suggests that the formation of cysts is due to structural defects in the collecting ducts, renal tubules, and their connecting regions during development. A blind-ended excretory duct connected to a functional glomerulus becomes a cyst. As these cysts enlarge, they compress adjacent kidney parenchyma, causing ischemia that impairs function and obstructs normal tubules, ultimately leading to progressive renal damage.
bubble_chart Pathological Changes
Grossly, the kidneys are enlarged with surfaces covered by cysts of varying sizes. On sectioning, the cysts are seen scattered throughout the renal parenchyma, with rare calcification. The cyst fluid is often amber-colored but may be bloody. Microscopically, the cyst walls are lined by a single layer of cells, and the renal parenchyma shows peritubular fibrosis with evidence of secondary infection. The glomeruli are reduced in number, some of which exhibit hyaline degeneration. In adults, the tubular basement membranes appear markedly thickened.
bubble_chart Clinical Manifestations(1) Symptoms: The stretching of the renal vascular pedicle by an enlarged kidney due to obstruction, infection, or intracystic hemorrhage can cause unilateral or bilateral renal pain. Microscopic or gross hematuria is common and can be quite severe, though the exact cause remains unclear. Renal colicky pain may occur when blood clots or stones pass downward. Patients may notice an abdominal mass on their own. Infection (chills, fever, flank pain) is a common complication of polycystic kidney disease. Bladder irritation symptoms may be the initial presentation. As renal insufficiency develops, symptoms such as headache, nausea, vomiting, weakness, and weight loss may occur.
(2) Signs: One or both kidneys are often palpable and have a nodular surface. Tenderness may be present if infection is present. Hypertension occurs in 60–70% of patients, and evidence of cardiac enlargement may soon follow. Fever may appear with pyelonephritis or infected cysts. In the uremic stage, significant anemia and weight loss may be observed. Fundoscopy may reveal typical moderate to grade III hypertensive changes.
(3) Laboratory findings: Anemia may result not only from chronic blood loss but more commonly from the suppression of hematopoietic function associated with uremia. Urinalysis may show proteinuria, gross or microscopic hematuria, pyuria, and bacteriuria. Progressive impairment of urine concentration occurs. Renal clearance tests can reveal varying degrees of renal dysfunction. About one-third of polycystic kidney disease patients are diagnosed due to uremia.
(4) X-ray findings: On plain abdominal films, bilateral renal shadows are usually enlarged, sometimes up to five times the normal size. A kidney length exceeding 16 cm should raise suspicion of this condition. Excretory urography with tomography aids in diagnosis, as tomography can reveal multiple lucent cysts. In tomographic and retrograde pyelograms, the kidneys are often enlarged, and the calyces exhibit bizarre configurations (e.g., spider-like deformities): widened, flattened, enlarged, and often curved around adjacent cysts. These changes may be mild or absent in one kidney, leading to misdiagnosis as a tumor or other renal disease. With infected cysts, perinephritis may obscure the renal and psoas muscle shadows. Angiography may show tortuous small vessels around cysts and "negative" shadows (avascular areas) formed by the cysts themselves.
(6) Renal scintigraphy: Gamma scintigraphy will show an enlarged kidney with multiple avascular "cold spots."
(7) Ultrasound: Ultrasonography is superior to excretory urography and renal scintigraphy for diagnosing polycystic kidney disease.
(8) Instrumental examination: Cystoscopy may reveal cystitis when abnormal urinary components are present. Occasionally, ureteral orifice bleeding may be observed. Ureteral catheterization and retrograde pyelography are rarely performed. {|107|}
bubble_chart Treatment Measures
Conservative and supportive therapy can be adopted unless there are uncommon complications.
(1) General measures: Patients should follow a low-protein diet (protein intake of 0.5–0.75/kg/d) and be required to drink at least 3000 ml of fluid daily. Physical labor should be performed within one's capacity, and strenuous exercise is prohibited. When the patient is in the decompensated stage of renal insufficiency, treatment should follow uremia protocols. At this stage, hypertension should be controlled, and preparatory dialysis may be performed.
(2) Surgery: There is no evidence that removing cysts or relieving cyst compression can improve renal function. If a large cyst is found compressing the upper ureter, causing obstruction and further impairing renal function, it can be excised or aspirated. When the degree of renal insufficiency is life-threatening, dialysis or kidney transplantation should be considered.
This disease occurs in children and has a very poor prognosis. Most patients who develop clinical symptoms and signs after the age of 35-40 have a much better prognosis. Although there is considerable variation among individuals, these patients typically die within 5-10 years after diagnosis unless they receive effective dialysis or kidney transplantation.
(1) Pyelonephritis: This is a common complication of polycystic kidney disease, and its cause remains unclear. It may present without symptoms, with very few or no pus cells in the urine. Diagnosis can be made through smear staining or quantitative culture. Gallium-67 citrate scanning can determine the site of infection, including the location of abscesses.
(2) Cyst infection: This can cause pain and tenderness in the kidney area, along with fever. Distinguishing between polycystic kidney infection and pyelonephritis is not easy, and gallium scanning during this seasonal epidemic can be very helpful.
(3) Hematuria: In very rare cases, active and persistent gross hematuria may occur, which can even be life-threatening.
(1) Bilateral hydronephrosis (caused by congenital disorders or acquired ureteral obstruction): May present with bilateral flank masses and manifestations of impaired renal function. However, intravenous pyelography and ultrasound examinations will reveal significant differences from polycystic kidney disease.
(2) Bilateral renal tumors: This condition is rare but may closely resemble polycystic kidney disease on urography. When one kidney in polycystic kidney disease is smaller or urography does not show distortion, differentiation from unilateral renal tumors becomes difficult. However, tumors are often confined to a specific part of the kidney, whereas cysts in polycystic kidney disease are distributed throughout the entire kidney. Unilateral renal tumors may have normal overall renal function, whereas polycystic kidney disease often exhibits impaired total renal function. CT or renal angiography can be used to differentiate between these two conditions. Scintigraphy or ultrasound examinations also aid in differential diagnosis.
(3) Von Hippel-Lindau disease (cerebellar hemangiomatous cysts, retinal vascular tumor diseases, and pancreatic tumors or cysts): This condition may involve progressive development of multiple renal cysts or adenocarcinomas in both kidneys. Urography or renal tomography may show polycystic kidneys, and the diagnosis can be made based on other characteristic features. CT, angiography, ultrasound imaging, or scintigraphy can confirm the diagnosis.
(4) Tuberous sclerosis (paroxysmal spasms, intellectual disability, and sebaceous adenomas): Sebaceous adenomas often affect the skin, brain, retina, bones, liver, heart, and kidneys. Renal lesions are typically multiple and bilateral, with microscopic findings of angiomyolipomas. Urography in the uremic stage may suggest cystic kidney disease, but other characteristic features, along with CT and ultrasound findings, can aid in differentiation.
(5) Simple renal cysts: Usually unilateral and solitary, with normal overall renal function. Urography may show a single lesion, whereas polycystic kidney disease presents as bilateral and multiple lesions.
