A spongy (medullary) kidney is a congenital multicystic deformity of the renal collecting tubules of the malpigian pyramids, which renders the renal tissue a porous sponge. In case of complications (pyelonephritis and nephrocalcinosis), renal colic, pyuria, and hematuria are noted. Pathology is diagnosed with retrograde pyelography and excretory urography. Treatment for clinical symptoms is aimed at eliminating the negative consequences. If the conservative treatment is ineffective, stones are removed from the kidney, nephrostomy, kidney resection , and nephrectomy.
Bilateral defect
In spongy kidneys, in most cases there is a bilateral defect in the medullary substance, while cystic disorders of varying severity can partially or completely affect the renal papillae. Unlike polycystic, the spongy has the correct shape, smooth surface, even contours and a slight increase in size compared with the age norm. In the section, it has an extension of the renal terminal tubules with many small cysts and cavities in the pyramid region.
Dimensions
The size of the cysts ranges from 1 to 4 mm, increasing towards the center. With a spongy kidney, two types of cystic formations are noted - diverticulum protrusions into the lumen of the tubules, with a cylindrical epithelium, or closed cavities formed by combining small cysts that are isolated from the renal tubules and lined with flat epithelium. Cystic cavities often contain a yellowish clear fluid (in the absence of an inflammatory process), calcified calculi, and desquamated cells. As a result of leaching, small stones from the tubules can be observed in the calyx or renal pelvis.
Renal Tissue Transformation
Renal tissue in the area of the pyramids with spongy kidneys, as a rule, is fibrotic and dense, and with concomitant pyelonephritis, it often has an inflammatory transformation.
Calcification of the parenchyma of such a kidney (nephrocalcinosis) is considered a secondary disorder, since urinary stasis in the enlarged tubules and cystic cavities contributes to the deposition of calcium salts. With spongy kidneys, their work persists for a long time. And distortion of the parenchyma can provoke any infectious process, the progression of stone formation processes and a change in the patency of the urinary tract.
Causes of the disease
Most urological studies confirm that spongy kidneys (according to ICD-10 - Q61), as abnormalities of intrauterine development, are similar to polycystic kidneys in pathogenesis and etiology. Scientists also believe that the occurrence of this pathology is associated with a late violation of embryogenesis, and changes in the collecting tubules of the kidneys can be noted in the postnatal period. The hereditary nature of this disease is confirmed, but the type of inheritance is most often sporadic.
Spongy kidneys are observed mainly in older and middle-aged people, in most cases in men. Due to the long latent course of the pathological process in childhood, the disease is detected relatively rarely.
Symptoms of the disease
Usually, pathology is not clinically apparent over a long period of time. Symptoms develop in the age range of 20 to 40 years with the occurrence of various complications: the formation of stones in the cystic cavities, urinary tract infections and kidneys. The main clinical manifestations of complicated spongy kidneys are dull or paroxysmal acute pain in the lower back, micro- and macrohematuria, pyuria.
Papillary nephrocalcinosis is observed in this pathology in more than 62% of cases. Renal colic occurs as a result of the migration of small calculi from cystic cavities into the pelvis and calyx. The development of the inflammatory process due to the penetration of small stones into the pelvis-cup system and impaired outflow of urine can manifest itself as a periodic increase in temperature, impaired by urination. Rarely, in severe forms of urolithiasis and secondary recurrent infection, purulent fusion and death of the parenchyma can develop, which is manifested by symptoms of renal failure.
Diagnostic measures for this pathology
The diagnosis of spongiform kidneys is made by an extensive urological examination, the main method of which is excretory urography. On the urogram, one can see intensely contrasted, fan-shaped and mosaic-positioned cystic clustered cavities and the expansion of the collective tubules. Morphological changes in the spongiform kidney usually affect the medullary distal zone of the organ, and the cortical substance and the cortico-medullary zone remain, as a rule, unchanged.
In the cystic cavities located in the papillary zone, the contrast agent for x-rays lingers longer than in the cups, which indicates stasis in the collecting tubules. The development of nephrocalcinosis can be indicated by papillary calculi obscured by radiopaque substances .
Many people wonder if it is possible to see a spongy kidney on an ultrasound scan. We will talk about this below.
Retrograde pyelography
Retrograde pyelography is used somewhat less frequently in the diagnosis of the disease, since it is not always possible to determine changes in the expanded ducts of the kidney on pyelograms. X-ray studies of the kidneys are advisable when combining spongy kidneys with nephrolithiasis or nephrocalcinosis to detect microlites and calcifications located in the distal pyramids. In this case, the shadows of small calculi in the cysts of the papillae, partially or completely coinciding with the shadows of the cavities with an excretory urogram, are visualized in the survey images.
Is a medullary spongiform kidney determined by ultrasound? Ultrasound examination does not always allow you to see small cysts in the deep layers of renal tissue. Additionally, such a diagnostic measure allows you to determine the presence of stones, hematuria and pyuria.
Laboratory tests for spongy kidneys also help determine the presence of pyuria, hematuria, minor hypercalciuria and proteinemia.
Differential diagnosis of this disease is carried out with pathologies in which there is a polycystic lesion of the medullary tissue of the kidneys (polycystic kidney disease, cystic pyelitis, papillary necrosis, chronic pyelonephritis), as well as with nephrocalcinosis, kidney stone disease, tuberculosis.
A photo of the spongy kidney on ultrasound see below.
Therapy
Spongy kidneys - why is it dangerous?
With an uncomplicated pathological process and its asymptomatic course, no therapy is usually performed. In this case, the patient is shown preventive measures to reduce the likelihood of developing complications. In the clinical manifestation of spongy kidneys, treatment is focused on preventing the development of secondary infection in the urinary tract and metabolic disorders (subsequent deposition of calcium salts in the cystically altered tubules of the kidneys). When pyelonephritis occurs, a plentiful drink is prescribed, a diet low in calcium, prolonged antibiotic therapy.
In order to prevent the formation of iatrogenic infection, instrumental urological manipulations for patients with spongiform kidneys are indicated only in exceptional cases. Nephrostomy is necessary in case of complication of the pathological process with pyelonephritis or urolithiasis, as well as in the absence of the effectiveness of traditional treatment. With focal cystic deformities affecting individual segments of the kidneys, they are resected.
Organ removal
Organ removal (nephrectomy) is extremely rare and exclusively with unilateral lesions. Migration of small stones, which disrupts the outflow of urine, can be an indication for the surgical removal of calculi from the kidneys using nephrolithotomy, pyelolithotomy, percutaneous nephrolithotripsy, and remote nephrolithotripsy. In mild cases, the prognosis for spongiform kidneys is favorable. However, with the onset and progression of nephrocalcinosis and the attachment of a secondary infection, it may worsen over time. With the complete absence of treatment for the complicated process, this leads to the formation of pus in the kidney and further loss of the organ.