Flank pain

Background

• This page outlines the general approach to flank pain in the ED
• The most common cause is nephrolithiasis, but vascular emergencies (AAA, renal infarction) must be considered
• Flank pain may also be referred from intra-abdominal or retroperitoneal pathology

Classification by Abdominal pain location

Side-by-side comparison of quadrants and regions.

Chart of commonly reported referred pain sites.

RUQ pain	Epigastric pain	LUQ pain
Flank pain	Diffuse abdominal pain	Flank pain
RLQ pain	Pelvic pain	LLQ pain

Clinical Features

• Location: Pain between the costal margin and iliac crest, typically lateral to the paraspinal muscles
• Classic renal colic: sudden onset, severe colicky pain radiating from flank to groin/testicle/labia
• Associated symptoms may help differentiate cause:
  • Dysuria, frequency, hematuria → urologic cause
  • Fever, chills → pyelonephritis, perinephric abscess
  • Pulsatile abdominal mass, hemodynamic instability → AAA
  • Sudden onset with atrial fibrillation or recent MI → renal infarction
  • Nausea, vomiting common with both renal and GI causes
• Physical exam:
  • CVA tenderness
  • Abdominal exam for peritoneal signs, masses, or pulsatile mass
  • Testicular exam in males
  • Pelvic exam in females of childbearing age if gynecologic cause suspected

Differential Diagnosis

Flank Pain

• Vascular
  • Abdominal aortic aneurysm
  • Renal artery embolism
  • Renal vein thrombosis
  • Aortic dissection
  • Mesenteric ischemia
• Renal
  • Pyelonephritis
  • Perinephric abscess
  • Perinephric hematoma
  • Papillary necrosis
  • Renal cell carcinoma
  • Obstructive uropathy
    • May or may not be due to nephrolithiasis
  • Renal infarction
  • Renal hemorrhage
• Ureter
  • Nephrolithiasis
  • Blood clot
  • Stricture
  • Tumor (primary or metastatic)
• Bladder
  • Tumor
  • Varicose vein
  • Cystitis
• GI
  • Biliary colic
  • Pancreatitis
  • Perforated peptic ulcer
  • Appendicitis (appendix may be pushed to RUQ in pregnancy)
  • Inguinal Hernia
  • Diverticulitis
  • Cancer
  • Bowel obstruction
• Gynecologic
  • Ectopic Pregnancy
  • PID/TOA
  • Ovarian cyst
  • Ovarian torsion
  • Endometriosis
  • Mittelschmerz or benign ovulatory pain
• GU
  • Testicular torsion
  • Epididymitis
• Other
  • Shingles
  • Lower lobe pneumonia
  • Retroperitoneal hematoma, abscess, or tumor
  • Epidural abscess
  • Epidural hematoma
  • Rib contusion/fracture

Evaluation

• Urinalysis — hematuria supports urologic cause but absence does not exclude it (up to 15% of kidney stones have no hematuria)
• Pregnancy test in females of childbearing age
• BMP/Cr — evaluate renal function, especially if obstruction suspected
• CBC — if infection or hemorrhage suspected
• Lactate — if concern for ischemia or sepsis
• CT abdomen/pelvis without contrast — gold standard for nephrolithiasis and can identify most alternative diagnoses
• CT with IV contrast or CT angiography — if vascular emergency suspected (AAA, renal infarction, aortic dissection)
• Bedside ultrasound — can identify hydronephrosis, AAA; first-line in pregnancy
• Renal ultrasound — alternative to CT, especially in young patients or pregnancy

Management

• Pain control is the priority for renal colic:
  • Ketorolac 15-30 mg IV or IM — first line (NSAIDs are superior to opioids for renal colic)
  • IV lidocaine 1.5 mg/kg IV over 10 min — emerging evidence as adjunct
  • Opioids (e.g., morphine, hydromorphone) for refractory pain
• IV fluids — for hydration; aggressive IV fluids do NOT speed stone passage
• Alpha-blockers (tamsulosin 0.4 mg PO daily) for medical expulsive therapy of stones 5-10 mm
• Pyelonephritis: Antibiotics per guidelines (see Pyelonephritis)
• Emergent urology consult for: obstructed infected kidney (pyonephrosis), bilateral obstruction, solitary kidney with obstruction, or urosepsis
• If AAA suspected: emergent surgical consultation

Disposition

• Admit:
  • Infected obstructed kidney / urosepsis
  • Intractable pain or vomiting
  • Acute kidney injury
  • Vascular emergency (AAA, renal infarction)
• Discharge with follow-up:
  • Uncomplicated renal colic with adequate pain control
  • Stone <10 mm without complicating factors
  • Strain urine, urology follow-up within 1-2 weeks
  • Return precautions: fever, intractable pain/vomiting, inability to urinate

See Also

• Nephrolithiasis
• Pyelonephritis
• Abdominal aortic aneurysm
• Renal infarction
• Abdominal pain