Obstructive Uropathy

Obstructive uropathy   Obstruction to urine flow results in attendant stasis, which leads to an elevation in the urinary tract pressure. This impairs renal and urinary conduit functions. It is a common cause of acute and chronic renal failure If there is early relief of the obstruction, defects in the function usually disappear completely. However, chronic obstruction can lead to: o Permanent loss of renal mass (renal atrophy) o Reduced excretory capability o Enhanced susceptibility to local infection and stone formation Aetiology  Obstruction to urinary flow can result from intrinsic or extrinsic mechanical blockade as well as from functional defects not associated with fixed occlusion of the urinary drainage system Symptoms and signs     Varies depending on whether acute/chronic, unilateral/bilateral, complete/partial and the cause Typically presents with flank pain which is colicky and quite severe In the acute setting of bladder outlet obstruction, bilateral renal pelvic or ureteric obstruction, or unilateral disease in patient with a solitary functioning kidney, symptoms of prerenal azotemia can develop. In prolonged obstruction, symptoms of polyuria and nocturia can accompany partial urinary tract obstruction as result from impaired renal concentrating ability. Disturbance of NaCl transport in the ascending limb of the loop of Henle and osmotic diuresis per nephron lead to decreased medullary hypertonicity and, therefore, a concentrating defect. Therefore there are increased urinary output and often also acquired renal tubular acidosis, hyperkalaemia and salt wasting. History of dysuria, pain, infection or change in urinary volume is common. Frequency, urgency, hesitancy, dribbling is further seen in patient with benign prostatic hyperplasia. Clinical examination or urogenital tract can often reveal abnormality. Diagnosis History:  There is usually difficulty in voiding, with pain and possible infection and a change in the urinary volume Clinical examination:  Abdominal/genital inspection o Males – meatal stenosis or phimosis, female – vaginal, uterine or rectal lesions  Palpation o Distension of kidney or urinary bladder  Rectal examination o Enlargement of prostate nodularity, abnormal rectal sphincter tone, rectal or pelvic mass  Urinalysis o Haematuria, pyuria, bacteruria (urinary sediment often normal)  Blood test o Creatinine, PSA, tumour markers Imaging diagnostic procedures:  Abdominal X ray (good for detecting nephrocalcinosis or radiopaque stones)  Abdominal ultrasound  Abdominal CT scan  Intravenous pyelogram  Retrograde urography or anterograde urography  Voiding cystourethrogram  Renal nuclear scan  Magnetic resonance (MRI) Treatment   If there is suspected urinary tract obstruction, then a bladder catheter should be inserted Treatment should be initiated as soon as possible to minimise the damage to kidney function and structure. On a temporary basis, drainage is usually achieved via nephrostomy, ureterostomy or ureteral, urethral or suprapubic catheterisation. If patient have acute UTIs with the obstruction, they should be given appropriate antibiotics. Chronic or recurrent infection in an obstructed kidney with poor function may necessitate nephrectomy. Cause of obstruction should be investigated promptly and given appropriate treatment. Functional obstruction sec. to neurogenic bladder may be reduced by the combination of frequent voiding and cholinergic drugs. If obstruction is due to nephrolithiasis, the causes should be investigated and appropriate steps undertaken to avoid recurrence