In an adult with right‑shoulder pain referred from the abdomen (Kehr’s sign), what are the most common causes, appropriate diagnostic work‑up, and initial management?

Right Shoulder Pain Referred from the Abdomen (Kehr's Sign)

In an adult presenting with right shoulder pain referred from the abdomen (Kehr's sign), the most critical immediate step is to obtain right upper quadrant ultrasound to evaluate for biliary pathology, followed by contrast-enhanced CT if ultrasound is nondiagnostic or if life-threatening conditions such as splenic injury, hepatic pathology, or perforated viscus are suspected. 1

Understanding the Mechanism

Kehr's sign represents referred pain from diaphragmatic irritation transmitted via the phrenic nerve (C3-C5 dermatome), which shares sensory distribution with the shoulder region. 2, 3 This classic sign indicates intra-abdominal pathology causing peritoneal or diaphragmatic irritation. 4, 5

Most Common Causes by Frequency

Biliary and Hepatic Pathology (Most Common)

• Acute cholecystitis with diaphragmatic irritation from gallbladder inflammation, characterized by fever, leukocytosis, positive Murphy's sign, and RUQ tenderness 1
• Biliary colic causing transient cystic duct obstruction with pain radiating to the right shoulder or back 1
• Hepatic abscess (ruptured or intact) requiring urgent identification 1

Critical "Can't Miss" Diagnoses

• Ruptured ectopic pregnancy in women of reproductive age—mandates immediate pregnancy test before any imaging 1, 6
• Perforated viscus (gastric, duodenal, or colonic perforation) with free air and peritoneal contamination 5
• Splenic pathology (abscess, rupture, or infarction) causing left-sided diaphragmatic irritation 4
• Mesenteric ischemia presenting with severe pain out of proportion to examination 1
• Pulmonary embolism with diaphragmatic involvement 1

Other Important Causes

• Pneumonia with right lower lobe involvement causing diaphragmatic irritation 3
• Acute cholangitis presenting with Charcot's triad (jaundice, fever/chills, RUQ pain) requiring urgent biliary decompression 1
• Pancreatitis with inflammatory extension to the diaphragm 7

Diagnostic Work-Up Algorithm

Immediate Laboratory Testing

• Pregnancy test (beta-hCG) in all women of reproductive age before any imaging—this is mandatory 1, 7, 6
• Complete blood count to assess for leukocytosis suggesting infection or inflammation 7, 6
• Comprehensive metabolic panel including liver function tests to evaluate hepatobiliary disease 7
• Serum lipase to evaluate for pancreatitis 7, 6
• Lactate if mesenteric ischemia is suspected, though specificity is limited 6

Imaging Strategy

First-Line Imaging:

• Right upper quadrant ultrasound is rated 9/9 (usually appropriate) by the American College of Radiology and should be performed immediately 8, 1, 7
• Ultrasound provides 96% accuracy for gallstones, evaluates gallbladder wall thickening (>3mm), pericholecystic fluid, bile duct dilatation (>6mm), and hepatic abnormalities without radiation exposure 1, 7
• Ultrasound criteria strongly suggesting acute cholecystitis include: gallbladder wall thickness >3mm, pericholecystic fluid, gallstones/sludge, positive sonographic Murphy's sign, and gallbladder distension 1

Second-Line Imaging (When Ultrasound is Nondiagnostic or Complications Suspected):

• CT abdomen/pelvis with IV contrast is rated 6-9/9 (may be to usually appropriate) and should be obtained when ultrasound is equivocal, the patient is critically ill, or complications are suspected 1, 7
• CT demonstrates >95% sensitivity for detecting colonic, pancreatic, splenic, and hepatic diseases 1
• Never order non-contrast CT for suspected cholecystitis or pancreatitis—contrast is essential to detect gallbladder wall enhancement, pancreatic necrosis, and vascular complications 1

Alternative Second-Line Options:

• HIDA scan (cholescintigraphy) shows 96% sensitivity and 90% specificity for acute cholecystitis, outperforming ultrasound's 81% sensitivity and 83% specificity 1
• MRI with MRCP demonstrates 85-100% sensitivity for cholelithiasis/choledocholithiasis and is preferred in pregnant patients to avoid radiation 1, 7

Initial Management Based on Findings

If Acute Cholecystitis is Confirmed

• Uncomplicated cholecystitis: Early laparoscopic cholecystectomy within 7-10 days; single preoperative antibiotic dose is sufficient 1
• Complicated cholecystitis (perforation, abscess, gangrene): Laparoscopic or open cholecystectomy plus 4-day antibiotic course (piperacillin-tazobactam or ertapenem); extend to ≤7 days in immunocompromised patients 1

If Acute Cholangitis is Suspected

• Urgent biliary decompression is required when Charcot's triad is present with biliary dilatation on imaging 1
• Obtain CT or MRCP to evaluate bile ducts 1

If Sepsis or Organ Dysfunction is Present

• Mortality increases dramatically with sepsis progression: no sepsis 1.2%, sepsis 4.4%, severe sepsis 27.8%, septic shock 67.8% 8
• Initiate early antimicrobial therapy and consider emergent intervention based on SOFA score (≥2 points indicates organ dysfunction) 8

Critical Pitfalls to Avoid

Pitfall	Correct Approach
Skipping pregnancy test in reproductive-age women	Always obtain beta-hCG before imaging to avoid missing ectopic pregnancy and unnecessary radiation [1,7,6]
Ordering CT without IV contrast	Contrast is mandatory to detect gallbladder wall enhancement, pancreatic necrosis, and vascular complications [1]
Bypassing ultrasound and proceeding directly to CT	Ultrasound should be first-line unless patient is hemodynamically unstable; CT has only 75% sensitivity for gallstones [1]
Assuming sludge alone equals cholecystitis	Critically ill patients commonly have gallbladder sludge without true cholecystitis; require ≥2 ultrasound findings plus clinical features [1]
Delaying surgical consultation while awaiting additional imaging	If clinical diagnosis of acute cholecystitis is made, do not delay surgical consultation [1]
Relying on ultrasound sensitivity alone	Ultrasound has only 88% sensitivity for acute cholecystitis; if clinical suspicion is high despite negative/equivocal ultrasound, proceed to HIDA scan or CT [1]

When to Refer Urgently

Immediate emergency department or acute surgical referral if:

• Fever with leukocytosis suggesting acute cholecystitis or cholangitis 1
• Signs of peritonitis or hemodynamic instability 8
• Suspected perforation, abscess, or gangrenous cholecystitis 1
• Positive pregnancy test with concern for ruptured ectopic pregnancy 1