Obstructive urinary tract disease

　　Obstructive urinary tract diseases can be classified as acute or chronic, partial or complete, and unilateral or bilateral. They can occur at any level from the renal tubules (casts, crystals) to the external urethral orifice, resulting in increased intraluminal pressure, urinary stasis, urinary tract infection, and stone formation.

　　Male urethral obstruction can be caused by benign prostatic hyperplasia, prostate cancer, chronic prostatitis with fibrosis, foreign bodies, bladder neck contraction, or congenital urethral valves. Urethral and urethral orifice stenosis can be acquired or congenital. Female urethral obstruction is rare, but it can be secondary to tumors, radiotherapy, surgery, or the use of urinary tract instruments (usually repeated dilation).

　　Obstructive nephropathy (renal insufficiency, renal failure, or tubulointerstitial damage) can be caused by increased intraluminal pressure, local ischemia, or often accompanied by urinary tract infection. Inflammatory T cells and macrophages infiltration, autoimmune reactions to Tamm-Horsfall mucin of retrograde urine, and vasoactive hormones may also participate in the damage to the kidneys.

　　The pathological manifestations include dilated collecting ducts and distal renal tubules, as well as chronic tubular atrophy, with minimal damage to the glomeruli. Obstructive urinary tract diseases may not show urinary tract dilation and can occur in retroperitoneal tumors or fibrous encapsulation of the collecting system; the lesions are mild, with no damage to renal function, and urinary tract obstruction occurs within 3 days; the compliance of the collecting system is relatively poor and not easy to dilate. Two percent of children may develop obstructive urinary tract diseases, often with congenital urinary tract abnormalities.

　　Bladder retention, ureteral hydronephrosis, renal pelvis hydronephrosis, and renal papillary necrosis are common complications.

　　1. Hydronephrosis of the renal pelvis.Due to the obstruction of urine excretion from the kidney, accumulation, causing urine retention and increasing intrarenal pressure, resulting in gradual expansion of the renal pelvis and calyces, atrophy and destruction of renal parenchyma, collectively known as hydronephrosis.

　　2. Clinical manifestations of renal papillary necrosis:Depending on the type of underlying pathogenic factor, it can manifest as chronic renal function damage (which can be diagnosed by intravenous pyelography), or as acute fulminant sepsis. The chronic stationary phase usually has no obvious symptoms, only manifesting as renal function impairment, decreased renal concentrating function, pyuria, and proteinuria. Acute renal papillary necrosis usually manifests as acute fulminant Gram-negative bacterial sepsis, which may be complicated by acute renal failure. It is especially important to avoid the occurrence of acute renal papillary necrosis when urinary tract infection occurs on the basis of diabetes or chronic urinary tract obstruction.

　　All patients with unknown etiology renal insufficiency should be considered for obstructive urinary tract disease. The medical history may suggest symptoms of benign prostatic hyperplasia or precancerous lesions or symptoms of stone formation.

　　If there is a hint of bladder neck obstruction (such as suprapubic pain, palpable bladder, or renal failure in elderly males of unknown cause), bladder catheterization should be performed first. If there is a suspicion of urethral obstruction (such as stricture or valve), cystoscopy and cystourethrography should be performed to further investigate the possible causes and the severity of prostatic and bladder lesions.

　　Abdominal ultrasound is the preferred examination for most patients due to the avoidance of complications such as allergy and poisoning caused by radiographic contrast agents. However, if only minor criteria (collecting system opacification) are considered in the diagnosis, the false-positive rate can reach 25%. The combined use of ultrasound examination, abdominal X-ray film, and CT if necessary can diagnose >90% of patients with obstructive urinary tract disease.

　　By detecting an increased resistance index of the affected kidney (reflecting increased renal vascular resistance), Doppler ultrasound examination can usually diagnose unilateral urinary tract obstruction.

　　Before intravenous urography, radionuclide renal scanning, or retrograde imaging examination, patients should be administered appropriate diuretics (such as furosemide 0.5mg/kg intravenously) for diuresis to check the degree of renal pelvis effusion and the relative prolongation of emptying time.

　　Intravenous urography can clearly define the site of urinary tract obstruction and detect associated pathological conditions (such as renal papillary atrophy caused by previous infection or necrotic papillae), with a very low false-positive rate. However, the operation of intravenous urography is麻烦 and requires radiographic contrast agents. Intravenous urography is mainly used when there are horn-shaped stones or multiple renal cysts or para-renal cysts (ultrasound and CT usually cannot differentiate cysts or stones from renal pelvis effusion); when CT cannot clearly define the level of obstruction; and when urinary tract obstruction is suspected to be caused by stones, detached papillae, or blood clots, it is used to screen for urinary tract obstruction. In cases of acute obstructive urinary tract disease, the collecting system may not need to be dilated, but if there is a mechanical obstruction factor (such as a stone), it can be localized.

　　Antegrade or retrograde pyelography is usually used to relieve urinary tract obstruction, not for diagnosis. However, when the medical history strongly suggests functional or anatomical abnormalities, even without renal pelvis hydroureteronephrosis, delayed emptying time can also confirm it. Single dehydration can prolong the emptying time. When the pyelography shows that one kidney is non-functional, radionuclide scanning can determine the renal perfusion status and clearly identify the functional renal parenchyma.

　　The prevention of obstructive urinary tract diseases should be determined according to the etiology. Stones can be removed by shock wave lithotripsy, which is generally effective for stones measuring 7-15mm in size. For those who still have no effect after conservative treatment (drinking water, traditional Chinese medicine, etc.) in the lower and middle segments of the ureter, retrograde stone extraction under cystoscopy should be adopted. In some cases where the next day's function is affected or the above method cannot be successful, surgical removal is needed. Antibiotics are often needed to be used simultaneously. Many obstructive kidney diseases are not completely obstructed, but they can become more obvious due to secondary infection, edema, inflammatory secretions blocking, etc. After the use of antibiotics, obstruction can be significantly improved, but the dosage and choice of medication need to be adjusted according to the culture and renal function. For those caused by tumors and other reasons, chemotherapy or surgical treatment should be applied. For polyuria and other disorders caused by obstruction, timely correction of water and electrolyte imbalances should be made.

　　1. Urine examination:In cases of concurrent infection, leukocytes and pus cells may be present in the urine, and non-specific bacterial growth may be found in midstream urine culture. In cases of concurrent stones, red blood cells may be present in the urine.

　　2. Cystoscopy:In cases of lower urinary tract obstruction, cystoscopy can detect prostatic hyperplasia, bladder neck stenosis, bladder stones, and small bladders, small chambers, diverticula, and other lesions.

　　3. Urography:When stones are present, radiographs can show non-transparent stone shadows. In the case of upper urinary tract obstruction, there is often hydronephrosis on the affected side. Severe hydronephrosis often leads to renal function impairment and does not show shadows. Ureteral hydronephrosis can show enlargement and tortuosity. In cases of lower urinary tract obstruction, the bladder contour is irregular, and diverticula can show the size and location of the diverticula. Cystourethrography can show urethral stricture and valve lesions.

　　4. B-ultrasound examination:During upper urinary tract obstruction, the affected kidney often shows a liquid level segment, indicating hydronephrosis. In the presence of stones, stones and their acoustic shadows can be detected. In cases of lower urinary tract obstruction, varying degrees of residual urine can be measured in the bladder.

　　5. CT scanning examination:During upper urinary tract obstruction, CT scanning can not only measure renal hydronephrosis but also determine the thickness of the renal cortex, which is of great reference value for determining the treatment plan. CT scanning can also detect stone shadows and sometimes detect renal pelvis and ureteral tumors.

　　6. Renal function examination:In the early stage of obstruction, renal function is often unchanged. Unilateral upper urinary tract obstruction often leads to renal function impairment on the affected side, which can be indicated by indocyanine green test, renogram, and intravenous urography. Long-term obstruction of both upper urinary tracts and lower urinary tract strictures can lead to renal insufficiency in both kidneys, with elevated blood urea nitrogen and creatinine levels. The renogram can show renal function impairment or obstructive renal pattern.

　　7. Urodynamic examination:During lower urinary tract obstruction, the maximum urinary flow rate decreases (＜10ml/sec), and the intravesical pressure during micturition increases significantly (＞70cm water column).

　　1. The general principle of diet is to pay attention to the balanced intake of animal protein, grains, and vegetable fiber. A diet low in sugar, fat, and sodium is recommended (moderately limiting sodium intake, i.e., salt, can reduce the excretion of sodium, calcium, uric acid, and oxalate through the kidneys, which is beneficial to prevent the recurrence of kidney stones).

　　2. Increase water intake. For adult male patients, the water intake should be 2500-3000 milliliters per day, for female patients, elderly patients with normal cardiovascular and renal function, 2000-2500 milliliters per day, and for children, reduced accordingly. In summer, appropriate increase in water intake can maintain urine output of more than 2000-3000 milliliters per day.

　　3. It is not advisable to drink alcohol, as alcohol can increase uric acid levels and is also prone to cause urine concentration after drinking.

　　Most cases can be corrected, but delayed treatment can lead to irreversible kidney damage.

　　Prognosis varies depending on the condition causing urinary tract obstruction and whether there is a urinary tract infection. Generally, acute renal failure caused by ureteral stones is reversible, and renal function can be fully restored. In chronic progressive obstructive urinary tract diseases, renal insufficiency can be partial or irreversible. When timely and adequate treatment is provided, the prognosis of renal function is good.

　　Treatment includes the use of medication (such as hormone therapy for prostate cancer), instruments (such as endoscopes, lithotripsy), or surgery to remove obstructions. If renal function is impaired, urinary tract infection persists, or pain is severe, rapid drainage of renal pelvis hydrops should be performed. For severe obstructive urinary tract diseases, urinary tract infections and stones may require temporary drainage. Percutaneous techniques can be used in most cases. Urethral obstruction may require catheter drainage or urinary diversion. For some patients, an internal pigtail ureteral catheter can be placed for acute or long-term drainage. Active treatment of urinary tract infection and renal failure is necessary.

　　Patients with pain and positive renal imaging after diuresis should consider surgical treatment. For asymptomatic patients with positive renal imaging after diuresis but normal renal function or negative renal imaging after diuresis, no treatment is needed.