Urinary Tract Obstruction Flashcards
What is hydronephrosis?
dilation of the renal pelvis due to urethral obstruction
What are some ways the ureter can be obstructed?
- stone/clot formation
- mural tumor
- extra-renal compression by other organs, tumors, etc.
- neurogenic or denervated bladder
How can papillary necrosis cause ureteral obstruction?
via sloughed papilla
What things cause papillary necrosis?
diabetes, analgesic abuse,
and either sickle‐cell disease or even sickle cell trait when patients are significantly dehydrated
What are posterior urethral valves?
Posterior urethral valves
are an anomaly that sometimes occur in children. In this disorder, flaps of tissue can obstruct the urethra in males causing bilateral obstruction and renal failure.
What are the common locations for ureteral obstruction by stones and clots?
Those locations where the ureter takes in acute angle, such as the ureteral pelvic junction, the location where the ureter crosses the iliac vessels and then where it enters the bladder, at the ureterovesical junction.
How can you tell the approximate level of the obstruction?
The urinary tract is Y‐shaped, so obstruction proximal
to the bladder will cause dysfunction in one kidney only whereas obstruction distal to the bladder will obstruct both kidneys.
Generally obstruction of one kidney is fairly well‐tolerated in terms of overall excretory function, assuming that the
contralateral kidney is healthy. Still it’s not a good thing
What things cause retroperitoneal fibrosis?
- drugs
- chemicals
- inflammation
- hemorrhage
- association with IgG4 related disease.
CHADI
many more
What is commonly performed in patients with urinary tract obstruction?
Retrograde pyelography
In this procedure, a urologist places a cystoscope into the bladder and then cannulates the ureter from within the bladder. Radiocontrast is injected backwards, that is, in retrograde fashion, filling the ureter and, if the ureter is patent, the renal calyx.
This is what might be seen in a case of retroperitoneal fibrosis, but this technique is also useful in evaluating obstruction from other causes.
Continuing urine formation in the face of obstruction results in a progressive rise in intraluminal pressure. What are the mechanical consequences?
- dilation proximal to the obstruction
- eventually compression and thinning of the renal cortex with parenchymal atrophy over time
Continuing urine formation in the face of obstruction results in a progressive rise in intraluminal pressure. What are the early (4-6 hrs) functional consequences?
ureteral pressure and renal blood flow increase as vasodilative mediators such as prostaglandins are released in an attempt to maintain GFR
What are the later (6+ hrs) functional consequences?
Vasoconstrictors (renin, TxA2) are locally produced by the macula densa and constrict afferent arterioles leading to a gradual decline in GFR to about 20% within 24 hrs
What are the chronic functional consequences?
ischemia and inflammatory cytokines result in interstitial fibrosis
What then is the effect of acute unilateral obstruction on total GFR?
In the presence of a
normal contralateral kidney, serum creatinine concentration doesn’t change very much or
elevates only slightly. Filtration in the contralateral kidney increases to compensate.
Based on an animal model, however, measurement of the GFR may overestimate the true
degree of recovery. “In a rat model in which complete unilateral ureteral obstruction was
induced for only 24 hours, approximately 15 percent of nephrons were nonfunctional as
late as 60 days after release, a presumed reflection of irreversible injury. Despite this
nephron loss, the GFR returned to normal because of hypertrophy and hyperfiltration in
the remaining functional nephrons.”
T or F. Acute obstruction will likely produce acute symptoms, whereas chronic progressive
obstruction may be asymptomatic.
T.
