Polycystic kidney disease

Polycystic kidney diseases encompass a series of entities characterized by the generalized presence of cystic structures in different areas of the kidney. Cysts are membranous structures that develop abnormally in the body (in this case in the kidney) and that usually contain fluid inside.

Within kidney cystic diseases we differentiate:

• Autosomal dominant polycystic kidney disease
• Autosomal recessive polycystic kidney disease
• Spinal cystic disease
• Cacci-Ricci disease
• Multicystic kidney
• Acquired cystic kidney disease

It should be said that in the kidney there may be simple cysts that are completely inconsequential and whose finding is usually accidental when performing an ultrasound or a scan for some other reason. The vast majority are benign and should only be periodically checked, but if you are not sure of its benignity, you can perform a puncture, aspiration, or even remove it surgically.

How is it produced?

Autosomal dominant polycystic kidney disease is a hereditary disease that is transmitted through alteration of the PKD1 gene, located on chromosome 16 (85% of cases), or the PKD2 gene, located on chromosome 4 (15% of cases ). Mutations in these genes cause less than 10% of nephrons to turn into cysts that secrete fluid. They cause an increase in the size of the kidney, which is correlated with the deterioration of kidney function.

Autosomal recessive polycystic kidney disease is an inherited disease caused by an alteration in a gene on chromosome 6 that already appears in the fetus in one in every 10,000 live births. It is characterized by the appearance of elongated cysts, less than 2 cm in size, arranged radially in the renal medulla.

Spinal cystic disease includes two entities:

• Cystic disease of the adult, an autosomal dominant disease due to an alteration of a gene on chromosome 1
• Nephronoptysis, an autosomal recessive disorder due to a mutation in a gene on chromosome 2

Cacci-Ricci disease or sponge kidney is a non-hereditary disease characterized by the presence of dilations in the final parts of the urine collecting tubules, the tubules that collect the urine produced by the kidney and empty into the ureter. . It is associated with Ehlers-Danlos disease and congenital hemihypertrophy.

Symptoms

Autosomal dominant polycystic kidney disease usually presents predominantly between 20 and 40 years of age. It is characterized by pain in the lower back associated with visible hematuria, recurrent urinary tract infections, high blood pressure and, as the disease progresses, chronic kidney failure. Likewise, it is associated with urinary tract stones, intestinal diverticula, and inguinal hernias. Hypertension occurs in 60% of cases. In 40% of cases, it is associated with multiple liver cysts, which do not usually cause symptoms or alter liver function. Cerebral aneurysms, dilations of the arteries of the brain, can also occur in 5-10% of cases, for which a screening by magnetic resonance angiography should be performed, since these patients have a greater risk of suffering from subarachnoid hemorrhage.

Autosomal recessive polycystic kidney disease is usually associated with the presence of congenital liver fibrosis and dilation of the bile ducts within the liver, which is known as Caroli's disease. Symptoms vary depending on the age of onset:

In the perinatal or neonatal period, renal manifestations predominate, with hypertension, uremia, and chronic renal failure.

During childhood and youth, liver disorders stand out, presenting portal hypertension.

Cystic kidney disease is more common in adults and is characterized by polyuria, nocturia, and polydipsia. Chronic kidney failure appears in less than 30 years after the onset of symptoms.

Nephronoptysis, the other type of spinal cystic disease, is more frequent in young patients and presents a similar clinical picture, with polyuria, nocturia and polydipsia, but renal failure is earlier and appears in less than 10 years from the onset of the symptom. It is also associated with growth retardation, anemia, skeletal and central nervous system alterations, pigmentary retinopathy, and liver fibrosis.

Cacci-Ricci disease is characterized by inflammation and fibrosis around cysts that appear in the distal parts of the urine collecting tubules. It is usually asymptomatic and benign, but is frequently associated with stones that occur in these cysts, which can lead to nephritic colic, urinary tract infections, or episodes of hematuria. In the long term, it can cause a decrease in the concentration capacity of the urine, the elimination of potassium and the control of the pH of the urine.

The multicystic kidney is an extreme form of renal cystic dysplasia, that is, a disorder in which a large part of the kidney tissue has degenerated into cysts that are joined together by fibrous tissue. It is the most common cystic disease of childhood. They are kidneys that do not function and are associated with an obstruction of the union of the kidney with the ureter or with a congenital absence of the ureter. A large mass is palpable in the abdomen, predominantly due to involvement of the left kidney.

Acquired cystic kidney disease is caused by prolonged uremia in patients with chronic kidney failure, especially in patients on dialysis for more than three years. It is usually asymptomatic, but it can cause bleeding, hypotension and in some cases degenerate into malignant lesions.

Diagnosis

The main diagnostic method for a patient with a clinical picture compatible with cystic kidney disease will be ultrasound. This imaging technique will allow us to appreciate cystic lesions in kidney tissue and assess their characteristics in order to reach a diagnosis taking into account the clinical context of the patient. In the case of acquired cystic kidney disease, contrast scanning or magnetic resonance imaging are the best methods to see the alterations that occur in this entity.

In the case of autosomal dominant and recessive polycystic kidney disease and nephronoptysis, liver ultrasound will also be performed to assess its cystic or fibrous involvement.

In Cacci-Ricci disease, an intravenous ureterography will also be performed, a radiological technique in which a contrast is injected through the vein that is eliminated via the urinary route and allows to assess the structure and alterations of the urinary excretory system, appreciating the dilatations and the possible calculations that may exist.

Treatment

In the case of autosomal polycystic kidney disease, treatment will be symptomatic, with control of arterial hypertension (the main cause of mortality), possible infections with powerful antibiotic treatments, and alterations due to kidney failure. Brain aneurysms associated with autosomal dominant polycystic kidney disease will be operated on if their size is greater than 1 cm. In the case of portal hypertension in the recessive form, a portosystemic bypass will be performed.

In the two forms of medullary cystic disease and in Cacci-Ricci disease, the treatment will be merely symptomatic and to control possible complications.

In the case of multicystic kidney, treatment is always surgical, removing the affected organ. In acquired cystic disease, the affected kidney will be removed if there are lesions larger than 2 cm; In this entity, the involvement is usually bilateral, so removal must be bilateral, leaving kidney transplantation as an option.

Precautionary measures

Since many of these diseases are genetic in origin, nothing can be done to prevent them. In the case of acquired cystic kidney disease secondary to chronic kidney failure, preventive measures are based on proper daily hydration (1.5-2 liters) and a diet moderate in salt and fat.