Kidney III: Obstructions

Question 1

What are the consequences of urinary tract obstruction?

Answer 1

Hydronephrosis
Hydroureter
Increased risk of infection
Increased risk of stone formation
Kidney injury and renal failure

Question 2

List the causes of urinary tract obstruction.

Answer 2

Urinary calculi
Tumors and proliferative lesions
Benign prostatic hyperplasia (BPH)
Uterine/cervical tumors
Inflammation (ureter, bladder, urethra)
Sloughed papillae
Blood clots
Pregnancy
Urethral atresia
Posterior urethral valves (PUV)
Urethral strictures
Bladder neck obstruction
Severe Vesicoureteral reflux (VUR)
Aberrant renal artery
Ureteropelvic junction narrowing/obstruction (UPJO)

Question 3

Which causes of urinary tract obstruction are more likely to cause bilateral obstruction?

Answer 3

Benign prostatic hyperplasia (BPH)
Uterine/cervical tumors
Severe Vesicoureteral reflux (VUR)
Functional disorders (Diabetic neuropathy, spinal cord damage)
Pregnancy

Question 4

What is the clinical presentation of urinary tract obstruction?

Answer 4

Often manifests as pyelonephritis
Many anomalies are asymptomatic
Some may be diagnosed in prenatal ultrasound
Some are diagnosed during evaluation of urinary tract infection or trauma

Question 5

List four types of common urinary calculi.

Answer 5

Calcium Oxalate and Phosphate
Magnesium Ammonium Phosphate (Struvite)
Uric Acid
Cystine

Question 6

Which type of urinary calculi is the most common?

Answer 6

Calcium Oxalate and Phosphate (70% of all stones)

Question 7

What are the causes of Calcium Oxalate and Phosphate calculi?

Answer 7

Hypercalciuria without hypercalcemia
Hypercalcemia and hypercalciuria
Increased uric acid secretion
Hyperoxaluria
Hypocitraturia
Idiopathic causes

Question 8

What are the causes of Magnesium Ammonium Phosphate (Struvite) calculi?

Answer 8

Associated with urinary tract infections by urea-splitting organisms
Alkaline urine due to urea splitting

Question 9

What are the causes of Uric Acid calculi?

Answer 9

Hyperuricemia
Hyperuricosuria
Idiopathic causes
Acidic urine pH < 5.5

Question 10

What are the causes of Cystine calculi?

Answer 10

Genetic defect in renal reabsorption of amino acids
Liver disease
Acidic urine

Question 11

What is the pH of urine in which Calcium Oxalate and Phosphate calculi form?

Answer 11

Near neutral or acidic pH

Question 12

What is the pH of urine in which Magnesium Ammonium Phosphate (Struvite) calculi form?

Answer 12

Alkaline urine

Question 13

What is the pH of urine in which Uric Acid calculi form?

Answer 13

Acidic urine (pH < 5.5)

Question 14

What is the pH of urine in which Cystine calculi form?

Answer 14

Acidic urine

Question 15

How do Calcium Oxalate and Phosphate calculi appear on plain film of the abdomen?

Answer 15

Radiopaque

Question 16

How do Magnesium Ammonium Phosphate (Struvite) calculi appear on plain film of the abdomen?

Answer 16

Radiopaque

Question 17

How do Uric Acid calculi appear on plain film of the abdomen?

Answer 17

Radiolucent

Question 18

How do Cystine calculi appear on plain film of the abdomen?

Answer 18

Faintly radiopaque

Question 19

What is the unique morphology of Calcium Oxalate and Phosphate calculi?

Answer 19

Dumbbell or envelope-shaped crystals

Question 20

What is the unique morphology of Magnesium Ammonium Phosphate (Struvite) calculi?

Answer 20

Rectangular coffin lid-shaped crystals; can form staghorn calculi

Question 21

What is the unique morphology of Uric Acid calculi?

Answer 21

Rhomboid or rosette-shaped crystals

Question 22

What is the unique morphology of Cystine calculi?

Answer 22

Hexagonal crystals

Question 23

What are the associations of cystine, crystaluria, and calculi?

Answer 23

Cystine: Genetic defect in renal reabsorption of amino acids
Crystaluria: Presence of crystals in urine
Calculi: Stones formed in the urinary tract

Question 24

What are the symptoms of urinary calculi?

Answer 24

Pain (renal colic, flank tenderness)
Hematuria
Vomiting, nausea
Frequent need to urinate
Urinating small amounts of urine

Question 25

What labs are involved in the evaluation of urinary calculi?

Answer 25

Imaging (CT scan) Metabolic panel for renal function Urinalysis for hematuria, pyuria, bacteria

Question 26

What are the consequences of obstruction in urinary tract calculi?

Answer 26

Hydronephrosis Hydroureter Increased risk of infection Increased risk of stone formation Kidney injury and renal failure

Question 27

What is Obstructive Uropathy?

Answer 27

Functional or anatomic obstruction of urine flow at any level of the urinary tract ## Footnote Can be partial or complete, unilateral or bilateral, and may present suddenly or insidiously.

Question 28

What is Hydronephrosis?

Answer 28

Dilatation of the renal pelvis and calyces (swelling of the kidney) ## Footnote Occurs due to obstruction in urine outflow.

Question 29

What is Obstructive Nephropathy?

Answer 29

Renal dysfunction caused by obstruction in urinary tract leading to kidney damage due to inflammation, tubular atrophy, and interstitial fibrosis.

Question 30

List consequences of obstructive uropathy.

Answer 30

* Hydronephrosis * Hydroureter * ↑ risk of infection * ↑ risk of stone formation * Kidney Injury * Renal Failure

Question 31

What are common causes of Obstructive Uropathy?

Answer 31

* Outflow obstruction * Urinary calculi * Tumors & Proliferative lesions * Benign prostatic hyperplasia (BPH) * Uterine/cervical tumors * Inflammation * Sloughed papillae * Blood clots * Pregnancy * Uterine prolapse & cystocele * Functional disorders

Question 32

What is the clinical presentation of Obstructive Uropathy?

Answer 32

Often manifests as pyelonephritis; many anomalies are asymptomatic ## Footnote Some may be diagnosed in prenatal ultrasound or during evaluation for urinary tract infection or trauma.

Question 33

What happens during Hydronephrosis?

Answer 33

Pressure builds up in the collecting system, leading to atrophy and vascular obstruction ## Footnote This triggers interstitial inflammation and fibrosis.

Question 34

What are the clinical features of Acute Obstruction in Hydronephrosis?

Answer 34

May present with pain; symptoms may depend on the cause of the obstruction ## Footnote For example, renal stone obstructing the ureter.

Question 35

What is the incidence of Urolithiasis in the US?

Answer 35

5-10% ## Footnote More common in males than females, with peak incidence in the 20s-30s.

Question 36

What are the symptoms of Renal Calculi?

Answer 36

* Pain * Renal colic * Flank tenderness * Hematuria * Vomiting * Nausea * Frequent need to urinate * Urinating small amounts

Question 37

What is the most common type of urinary stone?

Answer 37

Calcium oxalate and phosphate stones (70%)

Question 38

What causes Calcium Oxalate stones?

Answer 38

* Hypercalciuria without hypercalcemia (55%) * Hypercalcemia and hypercalciuria (5%) * Increased uric acid secretion (20%) * Hyperoxaluria (5%)

Question 39

What are the characteristics of Struvite stones?

Answer 39

Rectangular coffin lid shape crystals associated with UTI by urea-splitting organisms ## Footnote Commonly form in alkaline urine.

Question 40

What causes Uric Acid stones?

Answer 40

* Hyperuricemia * Rapid cell turnover (e.g., leukemia) * Diet rich in purines * Idiopathic cases

Question 41

What are Cystine stones and their causes?

Answer 41

1-2% of stones; hexagonal crystals ## Footnote Caused by a genetic defect in renal reabsorption of amino acids (cystinuria).

Question 42

Fill in the blank: The mechanism of calcium oxalate stone formation involves _______.

Answer 42

[nucleation of calcium oxalate by uric acid crystals in collecting ducts]

Question 43

True or False: All types of stones can potentially form staghorn calculi.

Answer 43

True

Question 44

What is the treatment for Uric Acid stones?

Answer 44

Alkalinization of urine and allopurinol

Question 45

What are the laboratory tests used in the diagnosis of Renal Calculi?

Answer 45

* Metabolic panel for renal function * Urinalysis for hematuria, pyuria, bacteria