Hydronephrosis Flashcards
1
Q
What is the blood supply of the kidneys?
A
- The renal artery supplies blood to the kidney and proximal ureter, as well as small branches off the gonadal artery and aorta
- The middle ureter is fed by blood vessels from the common iliac artery, internal iliac, superior vesical, middle rectal, and inferior vesical arteries
- Proximal to the iliac artery, the blood supply comes medially distal to the iliac artery; it comes laterally
2
Q
What are the significant regions of the ureter when it comes to obstruction?
A
- It is important to understand the blood supply of the ureter when contemplating surgery on it
- The ureter has a variable diameter of approximately 5-10mm but has 3 distinct areas of narrowing:
- the ureteral pelvic junction (2-3mm)
- the region over the iliac vessels (4mm)
- and the ureteral vesical junction (2-4mm)
- Stones, which typically form in the kidney, tend to hang up these areas of narrowing, causing obstruction and renal colic
3
Q
What are the three major categories of acute renal failure?
A
- Acute renal failure can be sub-categorized into 3 groups: prerenal, renal, and postrenal
- This lecture will deal with postrenal obstruction
4
Q
Define the following terms: hydronephrosis, obstructive uropathy, and obstructive nephropathy.
A
- Hydronephrosis: is a descriptive term referring to dilatation of the renal pelvis and calyces
- Obstructive Uropathy: is structural impedence to the flow of urine anywhere along the urinary tract
- Obstructive Nephropathy: refers to damage of the renal parenchyma resulting from obstruction of urine flow anywhere along the urinary tract
5
Q
What is the presentation of acute renal obstruction?
A
- Patients with acute obstruction typically present with:
- flank pain
- lower abdominal pain
- groin pain
- penile or testicular pain
- inner thigh pain
- nausea
- vomiting
- when infection is present:
- fevers and chills
- Serum studies may show azotemia and hyperkalemia
- Hematuria, proteinuria, and pyuria may be present in the urine. With bilateral obstruction patients are anuric.
6
Q
What are the phases of obstruction?
A
- Acute obstruction has 3 phases:
- Phase I: renal blood flow and ureteral pressure rise (1-1.5 hours)
- Phase II: decreased renal blood flow and increased ureteral pressure (1.5-5 hours)
- Phase III: decreased renal blood flow, decreased ureteral pressure (greater than 5 hours)
7
Q
Describe the process of recovery after kidney damage from obstruction.
A
- Damage to the kidney occurs gradually over a period of 6 weeks
- Studies in dogs have shown that with unilateral ureteral obstruction of 7 days, full recovery is possible within 2 weeks
- Fourteen days of unilateral ureteral obstruction results in permanent decline in renal function to 70% of control levels with 3-6 months necessary for recovery time
- After 4 weeks of unilateral ureteral obstruction, some recovery is possible
- After 6 weeks, no recovery is possible
- This is an important point when managing ureteral stones as patients can safely be followed for up to a week, allowing them time to spontaneously pass the stones
8
Q
What are the gross and histologic findings of an obstructed kidney?
A
- Grossly obstructed kidneys become hydronephrotic with compression of the papillae, caliceal blunting, and thinning of the parenchyma
- Histologically, there is dilatation of the tubules and glomerular hyalinization
9
Q
What is the presentation of chronic renal obstruction?
A
- Patients with chronic obstruction typically present with:
- weight gain
- edema
- malaise
- uremia (resulting in mental status changes, tremors and bleeding)
- and typically in males
- may have a weak or intermittent stream
- overflow incontinence
- polyuria secondary to a poor concentrating ability
10
Q
What are the diagnostic tests for renal obstruction?
A
- Obstruction is typically diagnosed by a variety of radiographic studies:
- Intervenous urogram / Pyelogram (IVU or IVP), which typically shows a delayed nephrogram, delayed pyelogram, hydronephrosis, columning, and in high-grade obstruction, forniceal rupture
- Ultrasonography shows dilated collecting system and echoic central areas in the normally eugenic renal sinus with parenchymal thinning
- Computerized tomography (typically shows findings similar to ultrasonography)
- Diuretic renography shows an elevated T1 half (clearance of tracer after Lasix) with less than 10 minutes considered normal, 10-20 min. elevated, greater than 20 min. indicative of obstruction
- Whitaker test is the gold standard for determining obstruction. Percutaneous infusion of saline in contrast into the renal pelvis at 10ml/minute shows a pressure gradient typically of less than 15cm of water. If the pressure gradient is greater than 22cm of water, this is indicative of obstruction
11
Q
What is post obstructive diuresis?
A
- Post obstructive diuresis refers to polyuria after release of bilateral obstruction
- It is the normal physiologic release of urea, sodium and water
- In pathologic conditions, there is impaired concentrating ability and sodium resorption
- If urine output is >200ml/hour for 2 hours, or the urine osmolality is low, or the patient is unable to drink, urine should be replaced at a rate of one half cc of D5.45 normal saline per cc of urine
12
Q
What is the presentation of a combination of obstruction and infection? What is the treatment?
A
- The combination of obstruction and infection can be deadly
- Typically, these patients have flank pain, fevers, chills, leukocytosis, pyuria and bacteri urea
- Urine enters the blood stream via pyelolymphatic and pyelovenous back flow
- Forniceal rupture may lead to a perinephric abscess, typically contained within Gerota’s fascia
- Patients with obstruction and infection should immediately have their blood and urine cultured
- Broad-spectrum intervenous antibiotics should be started and the obstructed kidney or bladder should be drained with percutaneous nephrostomy tubes, ureteral stents, or urethral catheters
13
Q
What is the presentation and etiology of urolithiasis?
A
- Urolithiasis occurs with supersaturation, crystallization and aggregation
- When the solubility product (Ksp) is reached, crystallization occurs
- More important is the formation product as urine is metastable with respect to calcium oxalate due to factors such as inhibitors, matrix, and nucleation
- Intrinsic factors causing urolithiasis are hereditary factors, age, and sex
- Extrinsic factors include geography, water intake, diet and occupation
- The etiology of stones in 95% of cases can be determined by a metabolic stone evaluation, which includes two 24-hour urine collections and blood tests
14
Q
What are the imaging findings of urolithiasis?
A
- 75% of stones are formed of calcium oxalate and calcium phosphate
- These tend to be radiopaque in nature and typically are caused from hypercalciuria, hyperoxaluria and hypocitraturia
- Magnesium ammonium phosphate (struvite) stones are the result of infection with urea-splitting bacteria and compose 8% of kidney stones
- These stones are radiopaque
- Uric acid stones occur in 6% of the population
- They are radiolucent and form in acid (pH5) urine
- Cystine stones are rare (2% of stones) and are secondary to homocystinuria
15
Q
What are the different types of stones and what are the diagnostic findings and predisposing factors?
A
-
Calcium oxalate with or without calcium phosphate
- 75%
- Opaque
- Hypercalciuria
- Hyperuricosuria
-
Pure calcium phosphate
- 9%
- Opaque
- Renal tubular acidosis
- Medications: Diamox, Calcium, Vitamin D
-
Magnesium ammonium phosphate (struvite)
- 8
- Opaque
- Infection with urea-splitting bacteria
-
Uric acid
- 6%
- Lucent
- Hyperuricosuria
- Acid urine
- Low urine volume
-
Cystine
- 2%
- Opaque
- Cystinuria
