A number of diagnoses can be confused with renal colic. The history and physical examination can help to narrow the differential. However, this may be difficult, since the patient's discomfort can interfere with the usual history and physical examination. Crucial to the evaluation of these patients is to ensure that a catastrophe mimicking renal colic is not missed.
The most critical alternative diagnosis to consider is an aortic dissection or ruptured AAA. Renal colic and AAA may have a similar presentation. Focal abdominal tenderness, abdominal distention, pulse disparity, and hemodynamic instability are not found in renal colic. These findings suggest a leaking or ruptured AAA. If a dissection or rupture is suspected, an emergency vascular surgical consultation should be obtained. If an AAA has not been excluded from the differential diagnosis, appropriate monitoring equipment, intravenous access, and professional staff should be sent from the emergency department with the patient for an imaging study.
Pyelonephritis may also cause flank pain; however the prodrome is less acute and the discomfort usually not as severe as renal colic. Fever is not a finding with kidney stones, and the urinalysis of renal colic does not demonstrate bacteriuria or pyuria in the absence of a concurrent infection. If renal obstruction is suspected concurrently with pyelonephritis, obstruction must be excluded by IVP, CT, or ultrasound. Antibiotics have poor penetration into an obstructed kidney. If infection in the presence of obstruction is confirmed, emergency urologic consultation for prompt obstruction relief should be obtained.
Papillary necrosis presents much as renal stones do. It is most frequently seen in patients with sickle cell disease, diabetes, nonsteroidal analgesic abuse, or infection. The urinalysis may appear to represent infection, with hematuria and pyuria. An IVP or CT can demonstrate sloughed renal papillae as a lucency within the renal pelvis. Urologic consultation and hospitalization are usually required.
Renal infarction, resulting from vascular dissection or arterial embolus, may present with acute flank pain. Urinalysis can demonstrate hematuria, and imaging will show decreased or absent function of the affected kidney. Emergency angiography is indicated. In renal vein thrombosis, there may be increased kidney size with decreased function. Urinalysis shows proteinuria and microscopic hematuria. All of these conditions require emergency urologic consultation.
Other pathologic conditions may cause compression or obstruction of the ureter, producing symptoms similar to those of renal colic. Any intrabdominal mass, including neoplasm or vascular structure, can potentially cause external compression of the ureter. A mass located within the urinary system may also cause obstruction and/or pain due to expanding size or in association with hemorrhage or necrosis. Therefore, a neoplasm is always within the differential diagnosis of renal colic.
Patients with severe abdominal pain out of proportion to the findings upon physical examination (especially if elderly or if the pain is in association with atrial fibrillation, congestive heart failure, liver disease, or low-flow vascular states) should raise suspicion of intestinal ischemia.
Gallstone pain can be very similar to that of renal colic and should generally be considered in all patients with any right upper quadrant abdominal tenderness. Unlike the symptoms of renal colic, biliary colic symptoms are often associated with oral intake, last for several hours before remitting, and include vomiting. Pancreatitis is suggested by left upper quadrant or midepigastric pain, especially in the presence of risk factors (e.g., alcohol consumption or cholelithiasis). A perforated peptic ulcer may present with severe pain in the midepigastrum or either upper quadrant. However, these patients have marked tenderness on examination and develop peritoneal signs over time. Appendicitis shares the unilateral presentation with renal colic, but the subacute prodrome usually excludes urolithiasis. Ventral hernias should also be considered in the differential diagnosis and sought on physical examination. Diverticulitis usually causes pain in lower quadrants, more commonly the left, and is associated with abdominal tenderness, fever, diarrhea, possibly hematochezia, but a more insidious prodrome than renal colic.
In women, gynecologic disorders can mimic renal colic. Ruptured ectopic pregnancy can present with acute pelvic and flank pain. A history of amenorrhea, tenderness on pelvic examination, and a positive pregnancy test result suggest this diagnosis rather than renal colic. Hemoperitoneum from a ruptured ectopic pregnancy may cause radiation of pain similar to that of renal colic as blood tracks along the abdominal cavity. Salpingitis usually has a more insidious onset, with cervical motion and uterine tenderness, and purulent discharge on pelvic examination. A tuboovarian abscess usually presents as salpingitis does, along with adenexal tenderness and mass on pelvic examination. An enlarging or ruptured ovarian cyst or ovarian or pelvic mass torsion should also be considered.
In men, other etiologies involving the genitourinary system must also be considered. Although renal colic can often cause pain radiating to the testicle, the findings on physical examination of the affected testicle should be normal. The presence of pain, redness, or swelling on examination should indicate another cause. Testicular torsion can present with the same sudden onset as renal colic; however, physical examination localizes the pathology to the testicle. Other entities, including infections such as epididymitis, prostatitis, and Fournier's gangrene, may have a more insidious onset, and the physical examination will differentiate them from renal colic. Finally, an incarcerated or strangulated hernia should be excluded by examination of the inguinal canals and scrotum.
Drug seekers may present with factitious episodes of renal colic. They can be remarkably inventive in the complexity of their ruse, and there is no specific method of detecting them. A history of multiple medical allergies to nonnarcotic analgesics and radiocontrast media is frequently given. Such patients may report having a known radiolucent stone and may simulate hematuria by placing blood in their urine. The vital signs may suggest this behavior if changes in blood pressure and heart rate do not match the extreme discomfort demonstrated. When the clinician is unsure, it is better to give analgesia than to deprive a patient suffering from true renal colic.
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