Urinary stones - Surgery Flashcards
Etiology of urinary stones (A++)
- Excess urinary calcium: Idiopathic, hyperparathyroidism, or prolonged immobilization.
- Excess urinary oxalates: Idiopathic, excess intake of food rich in oxalates.
- Excess uric acid: Gout, purine rich food like red meat and bean, or chemotherapy for malignancies.
- Excess cystine: Cystinuria is an autosomal recessive genetic defect that affects the proximal renal tubular reabsorption of cystine, ornithine, lysine, and arginine. All these amino acids are soluble in urine except cystine.
- Infection: Infection with urea splitting organisms makes the urine alkaline and infection stone formation.
Types of urinary stones (A++)
A. Calcium containing stones:
1. Calcium oxalate stone: the most common type. It is radio-opaque, formed in acidic urine.
2. Calcium phosphate stone: radio-opaque stone tend to form in relatively alkaline urine.
3. Infection stone (Struvite stone): radio opaque stone and form in alkaline urine. It is due to infection by urease producing organisms. The urease enzyme splits urea so ammonium is formed. Chemical analyses of the infection stones demonstrate the presence of Calcium, Magnesium, Ammonium, and Phosphate (three cations and one anion) so the term: triple phosphate stone is applied.
B. Non-calcium containing stones:
1. Uric acid stone: typically, radiolucent stone and formed in acidic urine. Uric acid stones represent about 10% of cases.
2. Cystine stone: A rare faint radiopaque stone appears as ground-glass in KUB. Formed in acidic urine and characterized by hexagonal cystine crystals in urine.
Clinical picture of Urinary stones (A++)
- Renal pain:
- Colicky in nature
- Sudden onset and offset
- In the flank
- Not related to posture
- Referred to ipsilateral testis, labia majora, or inner side of the thigh
- Upper GIT symptoms like nausea and vomiting.
- Usually there is history of similar attacks or stone passage.
DD of renal colic (B)
- Myalgia
- Radiculitis
- Appendicitis
- Intestinal obstruction.
Complications of urinary stones (B)
1- Obstructive nephropathy, calculus anuria, and renal failure.
2- Infection; pyelonephritis and pyonephrosis
3- Malignancy: rarely squamous cell carcinoma of the renal pelvis due to chronic irritation by long standing renal stone.
Investigations in Urinary stones (C)
Laboratory studies:
1. Urine analysis.
2. Renal function tests as blood urea and serum creatinine.
3. Uric acid, serum calcium, parathyroid hormone.
Imaging studies:
Imaging can detect the stone as a cause or the 2ry sign of obstruction. Radiographic features depend on the stone composition and vary according to modality
I. Plain X-ray of abdomen (KUB):
o Calcium containing stones: appear as radio opaque shadows similar to the bone.
o Non-calcium containing stones: not seen in the film or appear faint as in case of cystine stone due to sulfur content.
II. Abdominal ultrasonography (US):
The stone may be seen in the kidney, ureter or urinary bladder and appear as; Echogenic foci with associated posterior acoustic shadowing, or 2ry sign as hydronephrosis or hydroureter due to obstruction.
III. CT without contrast (Spiral CT):
o Spiral CT without contrast is the gold standard diagnostic tool. Now it is the preferred single imaging technique in emergency diagnosis of acute renal colic.
o In addition to the size and location of the stone and the overall health of the kidney, CT can also assess the density of the stone in Hounsfield units (HU).
IV. Intravenous urography (IVU)
- It is time consuming
- Contrast is nephrotoxic and not suitable in case of renal impairment.
- In cases of sever renal obstruction, the kidney will not excrete the contrast.
- This exam has been largely replaced by non-contrast CT.
Short note on CT in urinary stones (A++)
o Spiral CT without contrast is the gold standard diagnostic tool. Now it is the preferred single imaging technique in emergency diagnosis of acute renal colic.
o In addition to the size and location of the stone and the overall health of the kidney, CT can also assess the density of the stone in Hounsfield units (HU).
Advantages;
➢ It is a rapid procedure and no contrast is used.
➢ Very high diagnostic accuracy
➢ It can show all types of stones even radiolucent stones.
➢ Calyceal anatomy may be reconstructed
➢ Provide indirect signs on the degree of obstruction
➢ Provide information on non-urinary causes.
DD of radio-opaque calculi in X ray (b)
1) Phleboliths (calcified thrombi in pelvic veins).
2) Gall bladder stones overlying right kidney.
3) Calcified mesenteric lymph nodes.
4) Pancreatic calcification.
5) Renal artery calcification.
Treatment of kidney stones (A++)
- Medical treatment
For patient with acute renal colic: Pain relief is the first step. Non-steroidal anti-inflammatory drugs (NSAID) are effective in most of cases but morphine or pethidine may be required.
Chemolysis: Uric acid stones can be dissolved by using urine alkalizing agents orally for several weeks. In the case of presence of hyperuricemia, allopurinol should be prescribed. It blocks xanthine oxidase enzyme and reduces uric acid production. Also, low-purine diet (e.g. red meat and bean) should be advised. - Extracorporeal Shock Wave Lithotripsy (ESWL)
Extracorporeal means outside the body, Shock wave means strong pressure wave, lithos means stone, and tripsy means crushing. ESWL is a non-invasive outpatient procedure with mild sedations and may not need anesthesia. Shock waves generated outside the body are focused on the stone. The stone is precisely localized by x-ray, ultrasound, or both. Shock wave energy fragments the stone to multiple small size stones amenable for spontaneous passage with urine flow. Renal stone < 2cm in a patent urinary tract is suitable for ESWL. It is not suitable for large stone or in presence of distal obstruction. - Percutaneous nephrolithotomy (PCNL)
Create a tract to the kidney through the skin. Then introduce the nephroscope and fragment the stone under vision. Fragmentation of the stone can be carried out by one of the following:
a. Laser: Holmium: YAG laser lithotripsy.
b. Air force: Pneumatic lithotripsy.
c. Ultrasound: Ultrasound lithotripsy. - Open Surgery:
In modern urologic practice, Open surgery is rarely indicated because it needs prolonged hospital stay and carries risks of open surgery complications.
Ureteral stones treatment
The size of the stone is an important predictor of spontaneous passage. Hospital admission is necessary when any of the following is present:
o Oral analgesics are insufficient to manage the acute renal colic.
o Ureteral stone in a solitary or transplanted kidney.
o Ureteral stone in the presence UTI
- NSAIDs are recommended as the first line therapy for pain management over opioids.
- Antiemetic: Because nausea and vomiting frequently accompany acute renal colic.
- IV hydration for patients with clinical signs of dehydration
Treatment
- Alpha (α1) blockers help facilitate the passage of a small stone.
- ESWL is suitable for stone in the upper part of the ureter
- Endoscopy is suitable for stone in the lower part of the ureter
- Open surgery if the stone is associated with ureteral stricture.
Calcular anuria (B)
Calcular anuria means arrest of the urine flow from the kidney to the bladder because of obstruction of the both ureters / or the ureter of a single functioning kidney by calculi. It is a serious urologic emergency.
Investigations:
- Blood urea, serum creatinine, potassium level.
- Ultrasonography, KUB, and non-contrast spiral CT.
Treatment:
a. By pass the obstruction:
Endoscopic fixing a ureteric catheter or percutaneous nephrostomy under US guidance
b. Remove the obstruction:
Definite management of the stones after stabilization of general condition of the patient.
c. Manage the post obstructive diuresis if present.
BLADDER STONE (CYSTOLITHIASIS) (B)
Cystolithiasis is usually associated with urinary stasis as in cases of bladder outlet obstruction or neurogenic bladder dysfunction. Abdominal ultrasonography and plain x- ray (KUB) are good diagnostic tools.
Clinical presentation:
May be asymptomatic or presented with Frequency, Urgency, Nocturia, or Retention of urine.
Treatment:
-Cystotithotripsy: Endoscopic stone fragmentation and removal.
-Cystoltitotomy: Open surgical removal of the stone
Measures to prevent recurrence of kidney stones include (B)
Life style modification:
* Plenty fluid intake to guarantee diuresis of 2 to 2.5 L per day.
* Fluids should be consumed throughout the day.
* Overall, a balanced diet is ideal for preventing stone recurrence.
✓ High in fiber and vegetables
✓ Maintain normal calcium content (1.0 to 1.2 g per day). It is FALSE to advice low calcium diets.
✓ Limited sodium (5 gm/ d), fat, and animal protein (0.8 gm/ kg/d).
Citrate supplementation and diuretics:
Thiazide diuretics, allopurinol, and citrate supplementation are effective in preventing calcium stones that recur despite lifestyle modification, even in the absence of hyperuricemia, urinary acidosis, hypocitraturia, or hyperuricosuria.
If medication or citrate supplementation is prescribed, serum potassium levels and liver enzymes should be monitored to detect potentially adverse effects.
When immediate referral to a urologist is warranted (A++)
- Medical analgesia is insufficient.
- When sepsis is suspected or UTI with renal obstruction.
- Bilateral obstruction.
- When anuria is present.
- In women who are pregnant or have delayed menstruation.
- In patients who have potential comorbidities or > 60-year-old.
