Kehr’s sign is a clinical indicator characterized by referred pain in the shoulder—classically the left shoulder—resulting from irritation of the inferior surface of the diaphragm. In the context of emergency medicine and trauma surgery, a positive Kehr’s sign is highly suspicious for a ruptured spleen, though it can manifest in various conditions involving intra-abdominal hemorrhage or infection. This clinical finding relies on the complex neuroanatomy of the phrenic nerve and remains a vital, though sometimes overlooked, tool in the physical examination of patients with blunt abdominal trauma.

Understanding the Neuroanatomical Basis of Kehr’s Sign

To appreciate why an injury in the upper abdomen translates to pain in the shoulder, one must understand the "convergence-projection" theory of referred pain. The diaphragm is primarily innervated by the phrenic nerve.

The Role of the Phrenic Nerve

The phrenic nerve originates from the cervical spinal cord, specifically the C3, C4, and C5 nerve roots (often remembered by the medical mnemonic: "C3, 4, 5 keep the diaphragm alive"). These nerve roots provide motor supply to the diaphragm and sensory fibers to its central portion and the surrounding pleura and peritoneum.

Nerve Root Convergence

At the same time, the supraclavicular nerves, which provide sensation to the skin over the shoulder and the acromioclavicular region, also originate from the C3 and C4 nerve roots. When blood, inflammatory fluid, or air irritates the diaphragmatic peritoneum, the phrenic nerve transmits intense pain signals back to the spinal cord.

The brain, receiving these signals at the C3-C5 level, occasionally misinterprets the source of the stimulus. Because the sensory input from the shoulder occupies the same spinal segments, the patient perceives the pain as coming from the shoulder dermatome rather than the subdiaphragmatic space. This is why a patient with a massive splenic hematoma may complain of shoulder pain even if the shoulder joint itself is completely healthy.

How to Perform the Kehr’s Sign Test

Performing the Kehr’s sign test requires specific patient positioning to maximize the contact between abdominal irritants and the diaphragm. In clinical practice, the "test" is often part of a broader abdominal examination rather than a standalone maneuver.

Standard Patient Positioning

The patient is initially placed in a supine position (lying flat on their back). If the patient is hemodynamically stable, the examiner may observe for spontaneous complaints of shoulder pain. However, to elicit the sign more effectively, the examiner should use gravity to their advantage.

  1. Trendelenburg Position: Tilt the bed or elevate the patient’s legs significantly. This head-down, feet-up position encourages free-flowing blood or fluid in the peritoneal cavity to gravitate toward the upper quadrants, specifically under the diaphragm.
  2. Observation Period: The pain is not always instantaneous. In our clinical experience, it may take 2 to 5 minutes for sufficient fluid to accumulate against the diaphragmatic surface to trigger the phrenic response.
  3. Abdominal Palpation: Gently palpate the Left Upper Quadrant (LUQ). If the palpation increases the intensity of the shoulder pain, the test is considered strongly positive.

Saegesser’s Sign: The Phrenic-Point Test Variant

A related clinical maneuver is Saegesser’s sign, often used to confirm diaphragmatic irritation via direct pressure.

  • Technique: The clinician applies deep pressure with the thumb between the two heads of the sternocleidomastoid muscle or in the area of the phrenic nerve in the neck.
  • Positive Finding: If this pressure reproduces or exacerbates the abdominal pain or shoulder pain, it suggests a hyper-irritable phrenic nerve due to underlying abdominal pathology.

Clinical Significance and Differential Diagnosis

While Kehr’s sign is most famously associated with a ruptured spleen, it is a non-specific sign of diaphragmatic irritation. A meticulous clinician must consider several etiologies when this sign is present.

Splenic Rupture and Trauma

In the setting of blunt force trauma (such as a motor vehicle accident or a fall), Kehr’s sign in the left shoulder is a classic "red flag" for splenic injury. The spleen is highly vascular, and a rupture leads to rapid hemoperitoneum. Even a small amount of blood (as little as 50–100 mL) can irritate the diaphragm if the patient is supine.

Clinical notes suggest that Kehr’s sign is present in approximately 90% of patients with a documented splenic rupture. However, the absence of the sign does not rule out the injury, especially if the bleeding is contained within the splenic capsule (subcapsular hematoma).

Ectopic Pregnancy and Gynecological Emergencies

Kehr’s sign can be a crucial clue in the diagnosis of a ruptured ectopic pregnancy. If a fallopian tube ruptures, blood may fill the pelvis and eventually track up the paracolic gutters to reach the diaphragm. In these cases, the patient may present with lower abdominal pain and unexplained shoulder pain. This often leads to a misdiagnosis of a musculoskeletal shoulder injury if a thorough history is not taken.

Liver and Gallbladder Pathology

While Kehr’s sign is classically described on the left side, right shoulder pain can occur if the right side of the diaphragm is irritated. This is commonly seen in:

  • Liver Laceration: Following trauma to the right side of the abdomen.
  • Cholecystitis: Inflammation of the gallbladder can irritate the adjacent diaphragm.
  • Subphrenic Abscess: A collection of pus beneath the diaphragm, often following abdominal surgery.

Perforated Viscus

A perforated gastric or duodenal ulcer can release gastric contents or air into the peritoneal cavity. "Free air under the diaphragm" is a hallmark of perforation on imaging, but clinically, this air can compress the diaphragm and produce a positive Kehr’s sign.

Diagnostic Sensitivity and Specificity

Despite its long history in medical education, the exact sensitivity and specificity of Kehr's sign vary across clinical studies.

  • Sensitivity: High in cases of massive hemoperitoneum. In acute splenic rupture, various reports suggest a sensitivity ranging from 45% to 90%.
  • Specificity: Relatively low for a specific organ. While it confirms diaphragmatic irritation, it does not distinguish between blood, bile, pus, or air.

In modern emergency departments, the Kehr's sign test is largely a "screening" finding that prompts immediate imaging. It should never be used to definitively diagnose an injury in isolation, particularly when life-saving technology is available.

Why modern imaging complements the Kehr's sign test

In the era of the FAST (Focused Assessment with Sonography for Trauma) exam and high-resolution Computed Tomography (CT), the role of physical signs like Kehr’s has shifted.

The FAST Exam

A FAST scan can identify free fluid in Morison’s pouch, the splenorenal recess, and the pelvis within seconds. If a clinician elicits Kehr’s sign, the next logical step is an immediate bedside ultrasound to confirm the presence of fluid.

Computed Tomography (CT)

CT remains the gold standard for grading splenic or hepatic injuries. While Kehr's sign tells the clinician "something is irritating the diaphragm," the CT scan tells them "there is a Grade III splenic laceration with an active blush."

However, Kehr's sign remains invaluable in resource-limited settings or in the pre-hospital environment where advanced imaging is unavailable. It serves as a trigger for "high-acuity" triage.

What are the limitations of the Kehr's sign test?

There are several factors that can interfere with the accuracy of the Kehr's sign test:

  • Co-existing Shoulder Trauma: In multi-trauma patients, a fractured clavicle or a dislocated shoulder can mask the referred pain.
  • Analgesia: High doses of opioids administered in the field may blunt the patient's perception of referred pain.
  • Patient Positioning: Many trauma patients are kept in a cervical collar or on a backboard, making the Trendelenburg position difficult or contraindicated.
  • Slow Bleeding: If the hemorrhage is slow, it may take hours for enough fluid to reach the diaphragm, meaning the sign might be absent during the initial primary survey.

Case Study: Identifying a Positive Kehr’s Sign in the Field

Imagine a 24-year-old male involved in a side-impact collision. His primary survey reveals stable vital signs but tenderness in the left upper quadrant. During transport, he mentions that his "left shoulder is starting to ache," despite no direct impact on that area.

The paramedic, suspecting a splenic injury, slightly elevates the foot of the stretcher. Within three minutes, the patient reports that the shoulder pain has intensified and is now "sharp." This classic presentation of Kehr's sign allows the trauma team at the receiving hospital to bypass the waiting room and move directly to the trauma bay for a FAST exam and CT, potentially saving the patient from hemorrhagic shock.

How to perform Kehr's sign test in non-trauma cases?

In non-emergency settings, such as a patient with chronic abdominal pain, the Kehr's sign test is performed with less urgency but equal precision.

  1. Preparation: Ensure the patient has an empty bladder to allow for deeper palpation.
  2. Supine Evaluation: Assess for any baseline shoulder pain or range of motion issues to rule out local pathology.
  3. Gradual Elevation: Use pillows or an adjustable examination table to elevate the legs.
  4. Inspiration: Ask the patient to take a deep breath. As the diaphragm descends during inspiration, it comes into closer contact with abdominal organs. A positive Kehr's sign might only appear at the end of a deep inspiratory effort.

Frequently Asked Questions

Is Kehr's sign always on the left side?

Classically, yes, because it is most associated with the spleen. However, diaphragmatic irritation on the right side (from liver injury or gallbladder issues) will cause referred pain to the right shoulder. Both are manifestations of the same phrenic nerve mechanism.

Can Kehr's sign occur without a spleen injury?

Absolutely. Anything that irritates the diaphragm can cause it. This includes a ruptured ectopic pregnancy, a perforated ulcer, or even a subphrenic abscess.

How long does it take for Kehr's sign to appear?

It depends on the volume and rate of fluid accumulation. In a rapid splenic rupture, it may appear within minutes of the patient lying flat. In slower bleeds, it might take much longer.

What is the difference between Kehr's sign and Murphy's sign?

Murphy's sign is specifically for the gallbladder; the patient stops breathing in (inspiratory arrest) when the examiner palpates the gallbladder area. Kehr's sign is about referred shoulder pain due to diaphragmatic irritation.

Should I move the shoulder to check for Kehr's sign?

No. Kehr's sign is referred pain. Moving the shoulder will typically not change the intensity of Kehr's sign, but it might help you rule out a local shoulder injury. If moving the shoulder makes the pain significantly worse, the cause is likely orthopedic, not abdominal.

Summary

Kehr’s sign remains one of the most elegant examples of clinical neuroanatomy in practice. By understanding that a "shoulder problem" might actually be an "abdominal emergency," clinicians can significantly improve their diagnostic speed in critical situations.

  • Definition: Referred left shoulder pain due to diaphragmatic irritation.
  • Mechanism: Phrenic nerve (C3-C5) sharing spinal segments with supraclavicular nerves.
  • Primary Association: Splenic rupture or hemoperitoneum.
  • Key Maneuver: Placing the patient in the Trendelenburg position.
  • Modern Role: A screening tool that necessitates immediate follow-up with a FAST scan or CT.

In the fast-paced environment of emergency medicine, maintaining a high index of suspicion when a patient reports unexplained shoulder pain is essential. Kehr’s sign is not just a historical eponym; it is a physiological signal that internal bleeding may be occurring, requiring rapid intervention to ensure patient survival.