Urinary Tract Obstruction and Stone Disease

Question 1

Define urinary tract obstruction.

Answer 1

• Obstruction at any point between the kidney and urethral meatus.
• Can be:
  
  • partial or complete
  • unilateral or bilateral
  • acute or chronic

Question 2

What are the consequences of urinary obstruction?

Answer 2

• Hydronephrosis
• Pyonephrosis
• Hydroureter
• Obstructive nephropathy

Question 3

What are the causes of urinary obstruction:

• Inside the lumen?
• Within the wall?
• Outside?

Answer 3

Question 4

What are the most common causes of urinary obstruction in:

• Children?
• Female?
• Male?

Answer 4

Question 5

Which congenital disorders commonly cause urinary obstruction?

Answer 5

• Urethral valves (boys)
• Megaureter

Question 6

Describe retroperitoneal fibrosis and how it can cause obstruction.

Answer 6

• Inflammation / fibrosis of ureters and aorta encircles ureters leading to extraluminal ureteric obstruction (unilateral / bilateral).
• Systemic autoimmune disease (HLA association / IgG4 implicated).
• Mostly idiopathic.
• About 20% secondary to other causes: drugs, infection, iatrogenic.

Question 7

What are the symptoms of retroperitoneal fibrosis?

Which investigations should you do?

Answer 7

• Symptoms​
  
  • ​Weight loss
  • Malaise
  • Back pain
• Blood tests
  
  • ​CKD / CRP / ESR
• Imaging
  
  • ​CT will show medial deviation of ureters

Question 8

What are the malignant causes of urinary obstruction?

Where are they found?

Answer 8

• Tumours or nodes
  
  • Urothelial
  • Retroperitoneal
  • Pelvic
  • Colon

Question 9

Describe the pathophysiology of urinary tract obstruction.

Answer 9

• Ongoing urine production
• Increased pressure within the lumen
• Dilation proximal to obstruction
• Increased intratubular pressure + local ischaemia
• Thinning of renal parenchyma long term

Question 10

What might a patient with urinary tract obstruction complain of?

Answer 10

• Pain
  
  • ​Loin - can be worse with increased urine flow
• Urine output
  
  • ​Complete anuria
  • Polyuria with partial obstruction

Question 11

What might you find on examination of a patient with urinary tract obstruction?

Answer 11

• Pain / distress
• Signs of CKD
• Enlarged kidney
• Loin tenderness

Question 12

How would you investigate a patient with urinary tract obstruction?

Answer 12

• Urine dip
  
  • Blood
  • Leucocytes
  • Nitrates
  • Protein
• MSU - to look for infection
• Bloods
  
  • U&E / eGFR (to look for CKD / AKI)
  • PSA
  • CRP/ESR
• Imaging
  
  • USS
  • Plain AXR
  • Cross sectional imaging
  • IVU
  • Nuclear medicine studies (MAG3)
  • Interventional radiology: antegrade pyelography and ureterography
  • Cystoscopy

Question 13

Describe the management of urinary tract obstruction.

Answer 13

• Relieve the obstruction
  
  • ​Urinary / suprapubic cathater
  • Percutaneous nephrostomy
  • Stenting
• Post-obstructive diuresis
  
  • ​Massive diuresis as renal tubules lose their ability to reabsorb fluid.
  • Self-limiting but always monitor UO after any procedure to relieve obstruction.
• Treat underlying cause
  
  • ​Prostate disease
  • Steroids in RPF
  • Urethral valves
• Treat complications
  
  • ​Infections - ABx
  • Renal function - follow-up as can lead to CKD

Question 14

What is the outcome of urinary tract obstruction?

Answer 14

• Depends on underlying cause and stage of identification.
• Complete obstruction for weeks irreversible / partly reversible.
• Over months, the affected kidney is destroyed.
• Obstructive uropathy - 4% of end-stage renal disease.

Question 15

Describe kidney stones.

Answer 15

• Nephrolithiasis / urolithiasis
• Nephrocalcinosis - diffuse renal parenhymal calcification.
• Stones vary in size from small sand-like grains to staghorn calculi.
• Lifetime risk - 10%
• Often recurrent
• Male : female 2:1

Question 16

Describe the pathophysiology of kidney stones.

Answer 16

• Saturation of solute in urine.
• Inhibitors work to prevent stone formation in normal urine.
• Can be idiopathic or dur to underlying cause.

Question 17

What are the causes of urinary tract stones?

Answer 17

Question 18

What might you elicit in the history of a patient with urinary tract stones?

Answer 18

• Can be asymptomatic​
• Pain
  
  • ​Ureteric colic - severe
  • Loin-to-groin - reaches a peak in a few minutes
• Associated symptoms
  
  • ​Vomiting
• Urinary frequency
• Dysuria
• Haematuria

Question 19

What would you expect to find on examination of a patient with kidney stones?

Answer 19

• Restless / agitated
• Pallor
• Diaphoretic
• Pain
• Haematuria

Question 20

How would you investigate a patient with ?kidney stones?

Answer 20

• Urine dip
  
  • Protein
  • Blood
• Bloods
  
  • ​U&E
  • eGFR
  • Calcium
• Analysis of stone
• Imaging
  
  • ​Plain AXR
  • USS
  • IVU
  • CTKUB

Question 21

Why would you do these tests in a patient with kidney stones:

• Imaging?
• MSU?
• Stone analysis?
• Blood tests?
• Urine tests?

Answer 21

• Imaging
  
  • ​Identify a structural abnormality
• MSU
  
  • ​Look for infection
• Stone analysis
  
  • ​To establish type of stone
• Bloods
  
  • ​Serum calcium
  • Urate
  • Bicarbonate
• Urine tests
  
  • Urine calcium
  • Oxalate
  • Uric acid

Question 22

Describe the management of kidney stones.

Answer 22

• Renal colic - painful
  
  • Diclofenac
  • Opiate analgesia
  • Maintain UO
• Stones <0.5cm pass spontaneously
• Stones >1cm often need intervention
  
  • ESWL
  • Ureteroscopy with YAG laser
  • Percutaneous nephrolithotomy
• General advice
  
  • High fluid intake and maintain daily UO 2.5L
  • Reduce salt intake
  • Moderate protein intake
• Specific measures
  
  • Hypercalcuria - thiazide diuretics reduce Ca²⁺ excretion in the urine.
  • Infective stones - role for ABx.
  • Uric acid - Allopurinol.