Ch 37 UTO Flashcards
dilation of the renal pelvis and calices proximal to the point of obstruction
Hydronephrosis
refers to blockage of urine flow due to a functional or structural derangement anywhere from the tip of the urethra back to the renal pelvis that increases pressure proximal to the site of obstruction
Obstructive uropathy
functional or pathologic parenchymal damage in obstructive uropathy
Obstructive nephropathy
Between the ages of 20 and 60 years, urinary tract obstruction was more frequent among
Women
uterine cancer and pregnancy
Above the age of 60 years, UTO more common among?
Men
prostatic disease
Acute Upper urinary tract [ureter or ureteropelvic junction (UPJ)] obstruction may present with
Renal Colic
Acute Lower tract (bladder or urethra) obstruction may present with
Disorders of micturition
A common renal complication of multiple myeloma
Myeloma kidney or myeloma cast nephropathy
2 Intrinsic intramural processes that cause obstruction
- failure of micturition
- Failure of ureteral peristalsis (rare)
Drug that cause intrinsic intramural obstruction by interfering with bladder contraction
Anticholinergic agents
Drug which may mediate an α-adrenergic increase in urethral sphincter tone, resulting in increased bladder outlet resistance
Levodopa
Chronic use of this drug
can cause severe cystitis with subsequent ureteral obstruction
Tiaprofenic acid (Surgam)
Chronic infection of this organism leads to irreversible ureteral or bladder fibrosis and obstruction
Schistosomiasis (bilharziasis)
Which ureter is affected more in the temporary form of obstruction usually observed in pregnancy
Right
4 Conditions in pregnancy that may predispose to obstructive uropathy and acute kidney injury
- multiple fetuses
- polyhydramnios
- incarcerated gravid uterus
- solitary kidney
Second most common cause of extrinsic obstructive uropathy in women
Cervical AdenoCA
Preferred imaging to screen for obstructive uropathy in advanced cases of endometriosis
CT scan
most common cause of urinary tract obstruction in men aged 50 years and older
BPH
Top 2 most common causes of malignant genitourinary tumors causing urinary tract obstruction
- Cervical CA
- Bladder CA
Chronic pancreatitis with pseudocyst formation causes
left ureteral obstruction
Acute pancreatitis may result in
right-sided obstruction
Most common vascular cause of urinary obstruction
Abdominal aortic aneurysm
Retroperitoneal fibrosis usually involves which part of the ureter?
middle third
Elevated levels of these 2 risk factor proteins are present in the urine from obstructed kidneys
- neutrophil gelatinase-associated lipocalin (NGAL)
- β2-microglobulin
Preferred screening modality when obstruction is suspected
Ultrasonography
Ultrasonography is both highly sensitive and highly specific in detecting hydronephrosis, with the rates approaching
90%
Hydronephrosis detected as a dilated collecting system. On UTZ it appears as
anechoic central area surrounded by echogenic parenchyma
False negative results in UTZ (UTO) - 8
- first 48 hours of obstruction
- When hydronephrosis is absent despite obstruction evaluated by CT
- Dehydration
- Staghorn calculi
- Nephrocalcinosis
- Retroperitoneal fibrosis
- Misinterpretation of caliectasis as cortical cysts
- Tumor encasement of the collecting system
This new imaging technique provides information about renal stiffness related to fibrosis (i.e., chronic obstruction)
Renal elastography
Imaging used to differentiate between obstructive or nonobstructive dilatation of the collecting duct system
Duplex doppler ultrasonography
Diagnostic study of choice for the evaluation of the patient with acute flank pain
noncontrast-enhanced helical CT
Can visualize a dilated collecting system without the requirement for contrast enhancement
Non contrast CT
Exception to using a noncontrast CT
nephrolithiasis secondary to HIV protease inhibitors –> indinavir
Reason: These stones are not radiopaque, and signs of obstruction may be minimal or absent
thus the diagnosis may be missed with US and noncontrasted CT scan
Imaging to establish the diagnosis in Nephrolithiasis 2° to HIV protease inhibitor –> Indinavir
Contrast-enhanced CT
Imaging to diagnose upper urinary tract obstruction and providing information on the differential renal function (DRF) of both kidneys
Isotopic renography or renal scintigraphy
Clearance of the isotope from the collecting system which indicate obstruction
T½: < 15 minutes (normal)
> 20 minutes (obstruction)
15-20 minutes (equivocal)
In patients with severely impaired renal function, use of gadolinium during MRI results ro increased risk of developing this toxicity
Nephrogenic systemic fibrosis (NSF)
Because of the risk of NSF, gadolinium contrast media should be avoided in patients with what stage of CKD?
CKD stage 4 or 5
Defines the functional effect of upper urinary tract dilatation by measuring the hydrostatic pressures in the renal pelvis and bladder during infusion of a saline and contrast mixture into the renal pelvis via a catheter
Whitaker test
In whitaker test, what is the renal pelvic pressure that is considered obstructed?
Renal pelvic pressure (cm H2O):
< 15: nonobstructed
15 - 22: equivocal
> 22: obstructed
This procedure defines the lower level of the obstruction
Retrograde pyelography
This procedure establishes the proximal level of obstruction
Antegrade pyelography
Blocks the hyperemic response
Indomethacin
Critical to afferent vasodilation
Prostaglandins
Obstruction of the left kidney augments?
- AFFERENT renal nerve activity from the LEFT kidney
- EFFERENT nerve activity to the RIGHT kidney
2 phases of UUO
- Early hyperemic phase
- Late vasoconstrictive phase
Afyer how many hours does renal blood flow declines progressively in unilateral obstruction?
3 hours
After how many hours does renal plasma flow, GFR, and intratubular pressures have all dropped below normal values?
24 hours
The only cell death at early time points following the onset of obstruction, such as at 24 hours occurs at?
the very tip of the papilla, where focal necrosis may be observed
Following release of 24 hours of UUO, volume excretion from the postobstructed kidney, what happens tp the FeNa?
FENa may be twentyfold higher than normal
What is the effect of obstruction on membrane expression of transporter proteins responsible for apical sodium entry and of basolateral sodium exit
downregulates
major signaling mechanism by which obstruction downregulates Na+ transport
halt in urine flow
Represents a particularly important mediator of salt wasting in bilateral obstruction
ANP
This natriuretic peptide is markedly elevated in bilateral, but not in unilateral obstruction
ANP
