A 26-year-old man comes to the emergency department due to fever, right flank pain, and difficulty walking for the past 3 days. A week ago, the patient was treated with cephalexin for bacterial folliculitis. He was diagnosed with type I diabetes mellitus 10 years ago and takes subcutaneous insulin. Temperature is 38.9° C (102° F). During the medical interview, the patient lies supine on the examination table with his right hip and knee flexed and the limb externally rotated. On physical examination, he resists passive extension of the limb due to worsening of the pain. This patient's pathological process most likely involves which of the following muscles?

Question

A 26-year-old man comes to the emergency department due to fever, right flank pain, and difficulty walking for the past 3 days.  A week ago, the patient was treated with cephalexin for bacterial folliculitis.  He was diagnosed with type I diabetes mellitus 10 years ago and takes subcutaneous insulin.  Temperature is 38.9° C (102° F).  During the medical interview, the patient lies supine on the examination table with his right hip and knee flexed and the limb externally rotated.  On physical examination, he resists passive extension of the limb due to worsening of the pain.  This patient's pathological process most likely involves which of the following muscles?

Quizplus · Accepted Answer

11ec160b_35ec_df76_9249_17bbda812d15_MD0001_00 This patient most likely has a psoas abscess. The psoas muscle arises from the transverse processes and lateral aspects of the 12th thoracic through 5th lumbar vertebrae. It then courses downward across the pelvic brim anterior to the hip joint capsule and deep to the inguinal ligament to insert into the lesser trochanter of the femur via a tendon shared with the iliacus muscle. The iliacus and psoas muscles act as the major hip flexors. Psoas abscesses can occur due to direct spread of infection from an adjacent structure (eg, vertebral bodies, appendix, hip joint) or from hematogenous or lymphatic seeding from a distant and sometimes unknown site (in this case, the patient's skin infection). Risk factors include diabetes mellitus, intravenous drug use, HIV infection, and other forms of immunosuppression. Signs and symptoms of a psoas abscess include fever, back or flank pain, inguinal mass, and difficulty walking. Pain is exacerbated by movements that cause the psoas muscle to be stretched or extended (which causes irritation of the muscle fibers), such as extension at the hip (ie, psoas sign). As such, patients frequently position themselves to reduce discomfort by minimizing psoas stretching, particularly with hip flexion, external rotation, and lumbar lordosis. The psoas sign can also occur in acute appendicitis when the appendix is retrocecal (ie, located behind the cecum), as the inflamed appendix lies upon the right psoas muscle, causing irritation. (Choice A) The obturator externus runs from the obturator foramen of the pelvis to the trochanteric fossa of the femur. It acts to externally rotate the thigh. (Choice C) The quadratus lumborum courses posterior to the psoas muscle. It connects the 12th rib and upper lumbar vertebra to the iliac crest. Contraction of this muscle assists in extension and lateral flexion of the vertebral column. (Choice D) The rectus femoris is 1 of 4 quadriceps muscles that attach to the patella via the shared quadriceps tendon. It functions to extend the knee and flex the thigh. A patient with an abscess involving this muscle would most likely complain of thigh or knee pain and favor extension at the knee. (Choice E) The transversus abdominis is the deepest of the 3 anterolaterally coursing abdominal wall muscles. It helps maintain posture and increases intraabdominal pressure during forced expiration and defecation. Educational objective: Psoas abscess presents with fever, back or flank pain, an inguinal mass, and difficulty walking. Inflammation of the psoas muscle leads to pain with extension at the hip (ie, psoas sign). Psoas abscess can develop due to hematogenous or lymphatic seeding from a distant site, particularly in patients with diabetes mellitus, intravenous drug use, and immunosuppression (eg, HIV infection).

A 26-Year-Old Man Comes to the Emergency Department Due to Fever