A 62-year-old woman with a past medical history of breast cancer presented to the emergency department with three weeks of intermittent left scapula pain. The onset was at rest, and she had no history of trauma. The pain was not made worse or relieved by change in position. She denied any associated symptoms, but a review of systems revealed a few episodes of abdominal fullness over the preceding three weeks.
She denied chest pain, shortness of breath, abdominal pain, nausea, vomiting, diarrhea, fever, chills, leg pain or swelling, and recent travel. Prior treatment for the pain included over-the-counter analgesics, which offered minimal relief. She had outpatient evaluations by a cardiologist and a neurologist for her shoulder pain before her ED visit. The outpatient doctors ordered numerous blood tests, a transesophageal echocardiogram (TEE), and an MRI of the lumbosacral spine. The indications for these diagnostic modalities were unknown to the patient.
The TEE was unremarkable, and MRI showed a clinically insignificant lumbar disc herniation. The patient had bilateral lumpectomies in 2000 and 2002, and additional past medical history included palpitations and mitral valve prolapse. She denied tobacco, alcohol, or drug abuse. The patient's vital signs on arrival in the ED were unremarkable. She was uncomfortable, her abdominal exam included normal bowel sounds, and her abdomen was flat, not obese, not distended, and nontender without palpable organomegaly.
A back exam revealed no tenderness to palpation and no deformity. The remainder of her physical exam was normal. The patient received ketorolac, oxycodone/acetaminophen, and diazepam. Blood work was drawn, and a CT of the chest with contrast to rule out PE was obtained. The labs were unremarkable except for a mild normocytic anemia. The CT of the chest was extended to the abdomen during the exam at the order of the attending doctor when the CT technologist recognized a suspicious mass on the last cuts of the CT chest.
The abdominal CT revealed a large abdominal mass measuring 13 cm x 15 cm x 24 cm in size, encasing and displacing the abdominal aorta, inferior vena cava, and the left kidney, while extending from the left diaphragmatic crus to the left iliac fossa. The patient was admitted, and underwent percutaneous biopsy. The pathology was consistent with lymphoma. The patient was subsequently discharged home with oncology follow-up as an outpatient. She is now awaiting a specialized multifaceted treatment plan from her surgeon and oncologist.
Referred pain is found in the literature as early as 1893 when Sir Henry Head, an English neurologist, included the phrase “referred tenderness and pain” in his paper, “On Disturbances of Sensation with Especial Reference to the Pain of Visceral Disease.” (Brain 1893;16:1.) Since then, it has been defined as pain perceived at a site adjacent to or at a distance from the site of origin. (Clin J Pain 2001;17:11.)
Several neuroanatomical and physiological theories focus on this concept. Collective conclusions from past studies state that nociceptive dorsal horn and brainstem neurons receive convergent inputs from various tissues; therefore, higher centers cannot identify the actual input source correctly.
The best known example is pain experienced during a heart attack. Nerves from damaged heart tissue convey pain signals to spinal cord levels T1-T4 on the left side, which are the same levels that receive sensation from the left side of the chest and part of the left arm. Another example involves pain from a ruptured spleen or splenic abscess. Called Kehr's sign, it is the referred pain from abnormal spleen pathology irritating the diaphragm. The sensory fibers of one of the phrenic nerves send pain signals to the spinal cord at C3-C5. Neurons at these spinal cord levels also receive sensation from the shoulders via the supraclavicular nerves.
The patient in this case was experiencing referred pain from the large abdominal mass abutting the diaphragm, causing signals to be sent via the phrenic nerve to the brain and making the patient perceive the pain as coming from the shoulder. Unfortunately, the mass was not able to be palpated by physicians due to its posterior location in the abdomen nor was it readily distinguishable from the other abdominal organs because of the mass spanning across the entire abdomen from the diaphragm to the bony pelvis, making it critical to obtain a CT of the abdomen and pelvis.
It is important for physicians to remember the concept of referred pain when diagnosing and treating presumed musculoskeletal complaints, especially in instances when extensive diagnostic testing has elicited no cause. Had the symptom been considered before her ED visit, it may have led to the correct diagnosis and earlier intervention.