Nephrolithiasis

• Urologic stone disease is one of the most common disorders of the urinary tract, and one of the most common diseases seen in the ED.
• About 2-5% of the population will form a urinary stone during their lifetime.
• Several factors correlate with an increased incidence of stone formation: men greater than women (3:1 ratio), age between 20 and 50 yr, a sedentary lifestyle, warm weather (peak incidence during the hottest 3 mo) and residence in the Southeastern United States.
  Table Types of renal stones

  Stone Type	Composition	Incidence	Risk Factors
  Calcium	Calcium oxalate or Calcium phosphate	75%	Hypercalciuria (secondary to increase ingestion of antacids, milk and vitamins C, A, D, bone disease, immobilization, PUD) Hyperparathyroidism Hyperoxaluria (secondary to small bowel disease, jejunoileal bypass surgery) Familial history Dehydration Diet-ingestion of high oxalate foods such as coffee, cola drinks, beer, citrus fruit, spinach, high dose vitamin C
  Struvite	Magnesium Ammonium phosphate	15%	Chronic kidney infection UTI with urea-splitting bacteria (Proteus, Klebsiella, Pseudomonas species) Persistent alkaline urine (pH 7.6) Usual composition of "staghorn" calculi
  Uric acid	Uric acid	10%	Increase urinary uric acid excretion (acidic urinary pH) secondary to diet high in purines such as organ meats, dried legumes,fish
  Cystine	Cystine	1%	Associated with rare hereditary disorder- cystinuria

  
  
• In addition, there is increased genetic predisposition seen within families.
• Nephrolithiasis is a recurrent disease for most people with 37% developing another stone within 1 yr, 50% within 5 yr, and 70% within 9 yr.
• There are four basic types of renal stones (Table 6.1):
• calcium
• struvite
• uric acid
• cystine
• Retrieval and subsequent analysis of the stone is important to determine possible causes of stone formation and guide future therapy.

Clinical Presentation

• The classic presentation of renal colic is a history of abrupt onset of severe, crescendo flank pain that eventually radiates into the lower abdomen and ipsilateral testes or labia as the stone progresses down the ureter.
• The patient is often found writhing in bed, unable to find a comfortable position.
• This is in marked contrast to the patient with peritonitis who will be lying completely still avoiding any movements.
• The pain is colicky in nature, waxing and waning, but rarely absent.
• Nausea and vomiting are almost always present, and abdominal distension with an ileus is not uncommon.
• A history of fevers or chills is suggestive of infection and should be aggressively pursued.
• About one-third of patients will give a history of gross hematuria.

Diagnosis

• The most important laboratory test to obtain in this clinical setting is the urinalysis.
• Hematuria is almost always present, although there is no correlation between the degree of hematuria and the extent of ureteral obstruction. In fact, about 20% of patients with documented ureterolithiasis on IVP have no microscopic hematuria.
• Pyuria can be seen in the absence of infection and is probably the result of ureteral inflammation. However, the finding of bacteruria implies urinary tract infection and always requires further investigation, especially if fever and chills are present.
• A urine culture should always be sent when infection is suspected. A serum WBC >15,000 suggests an infectious etiology, while mild leukocytosis without concominant fever usually represents demargination, testicular torsion.
• Some authors also recommend obtaining a serum uric acid level, as it will be elevated in 50% of all patients with uric acid stones, and a serum calcium to screen for hyperparathroidism and other disorders of calcium metabolism.
• Other important laboratory tests include CBC, serum electrolytes, BUN and creatinine.

Radiographic Studies

• The IVP has both high sensitivity and specificity, establishing the diagnosis of calculous disease 96% of the time.
• While a flat plate of abdomen (kidney, ureter, and bladder, or KUB) is the standard scout film done prior to an IVP, alone the KUB is not a reliable study to diagnose renal stone disease.
• Contraindications to radio contrast medium are known allergy to contrast dye and renal insufficiency.
• Other studies that can be used in patients who cannot tolerate IV are helical CT, ultrasound and renal scan. (See Renal Colic on page 507 of this volume.)

Differential Diagnosis

• The key is not to miss a life-threatening condition, such as rupturing abdominal aortic aneurysm (Table 6.2).
• A careful history and physical exam can frequently elucidate the underlying pathology.

Management

• The mainstay of therapy for ureterolithiasis is IV hydration, analgesia, and antiemetic, if needed. Hydration can be initiated with IV crystalloid infusion of 1 L NS over 30-60 min, and then 200-500 ml/h.
• Patients presenting with renal colic are in severe pain and often require significant amounts of narcotic analgesics (morphine sulfate or meperidine in age and weight determined doses).
• NSAIDs, particularly ketorolac, are frequently used in conjunction with narcotics as they are thought to decrease pain by diminishing ureterospasm and renal capsular pressure.
• Pain medication should be administered promptly while awaiting the results of further tests.
• Most patients with uncomplicated renal stone disease, whose pain is adequately controlled and can tolerate oral fluids can be discharged home without patient urologic follow-up and careful instructions, periuethral abscess.
• All patients should be given a urinary strainer and instructed to strain all urine for up to 72 h following cessation of pain.
• Patients should be instructed to return to the ED immediately for any fever and chills, persistent nausea and vomiting, or for intractable pain, not relieved by prescription oral narcotics.
• Urologic follow-up should be arranged within 1-2 wk.
  Table Differential diagnosis of renal colic

  Abdominal Aortic Aneurysm	May have similar clinical presentation, with gross or microscopic hematuria	Contrast CT scan or angiogram, if stable
  (dissecting or rupturing)	More likely in older males May present with hypotension Palpate for pulsatile abdominal mass with focal tenderness Listen for bruit Palpate distant extremity pulses
  Acute Pyelonephritis	Mild to severe flank pain, although typically not as acute as renal colic More prolonged prodrome, with fever Urinalysis shows pyuria and bacteruria CAUTION: renal obstruction with pyelonephritis is a urologic emergency requiring prompt consultation	IVP (or other radio- graphic imaging) if obstruction suspended
  Papillary Necrosis	Secondary to passage of sloughed papillae down ureter Seen in patients with sickle cell disease, diabetes, NSAID abuse, or history of acute or chronic UTI UA can show hematuria and pyuria Requires urologic consultation with possible admission	IVP-may show sloughed renal papillae as a lucency within renal pelvis, but may also mimic a stone
  Renal Infarction
  1. Renal artery embolism	Presents with acute flank pain and hematuria renal Most common acute renal vascular event Most often of cardiac origin-atrial fibrillation, acute bacterial endocarditic mural thrombus	IVP shows absent function
  2. Renal artery aneurysm	Also presents with acute flank pain and hematuria Usually small and clinically not significant Dissection or rupture is rare-but will cause shock	Emergent angiography indicated
  3. Renal vein thrombosis	Acute flank pain with hematuria and proteinuria Predisposing factors are nephrotic syndrome, malignancy, and pregnancy Emergent urologic consultation is required for all cases of renal infarction	IVP shows decreased renal function and increased renal size
  Ectopic Pregnancy	Unilateral abdominal pain History of amenorrhea, abnormal vaginal bleeding May present with shock	Pregnancy test required in all women of child-bearing years
  Appendicitis	Unilateral presentation Sub acute prodrome Abdominal tenderness with guarding or rebound	Laboratory tests and physical exam; if diagnosis still in question-CT scan with oral contrast

• There are several situations in which admission is indicated:

1. Acute obstruction with concurrent infection. The finding of fever, pyuria, or bacteruria in a patient with renal colic requires further work-up and admission.
   Urine and blood cultures should be obtained and intravenous antibiotics, covering the usual urinary pathogens, should be promptly started while in the ED. Urologic consultation is required.
2. Solitary kidney with complete obstruction. Patients with only one kidney become essentially anaphoric with complete obstruction and may require surgical drainage.
   Emergent urologic consultation and admission are required.
3. Uncontrolled pain. Patients whose pain can only be controlled by intravenous analgesia require admission.
4. Intractable emesis. Patients who are unable to tolerate oral fluids must be admitted for IV hydration.
   Other scenarios, which may or may not require hospitalization, but should be discussed in consultation with a urologist are: patient with underlying renal insufficiency, dye extravasasation demonstrated on IVP, large stone size, and high grade obstruction.