ACEP ID:

Pediatric Emergency Medicine

Pearls & Pitfalls - Positive Psoas and Obturator Signs: They Don’t Always Indicate Appendicitis

Davis L. Mellick, PA-C,
Department of Emergency Medicine,
Medical College of Georgia, Augusta;

Rachel Milner, PA-S,
School of Allied Health Sciences,
Medical College of Georgia, Augusta
 

Pearl:A patient complaining of lower abdominal pain with a positive psoas and obturator sign does not necessarily have appendicitis. Lower abdominal pain with positive psoas and obturator signs can also be found with an iliopsoas muscle strain and other less common conditions.

Presentation: A 16-year-old girl presented to the emergency department with progressively worsening right suprapubic pain that began a few days prior to presentation. The pain was sporadic and worsened with activity. With menstrual cycles, the pain was severe enough to be incapacitating. Her history was significant for a left nephrectomy and right ureteral implant in 1998 to manage repetitive urinary tract infections. She denied any complications of her surgeries or recurrence of symptoms. While the patient complained of chills, she was afebrile in the emergency department. She did not have anorexia, nausea, vomiting, or diarrhea, or any history of trauma or acute injury. On physical exam, she showed no abdominal pain at rest; however, the abdomen and back were significantly tender to palpation. Both the psoas and obturator signs were positive. Urinalysis was normal with no evidence of renal disease or of an infectious process. Her beta hCG was negative. The patient’s white blood cell (WBC) count was normal, as were all values of her complete metabolic panel (CMP). Based on the severity of the patient’s presentation, a CT scan was ordered by the first attending physician. The CT was read as negative for any intra-abdominal pathology. At the change of shift, the oncoming physician repeated the physical examination and was able to localize the pain to the lower back and lower abdomen. (Figure 1) A diagnosis of iliopsoas muscle strain was made.

Discussion: For a patient presenting with right lower quadrant (RLQ) pain, appendicitis is one of the most pressing diagnoses to rule out before moving on to other potential diagnoses. Classically, appendicitis presents with RLQ pain, anorexia, nausea and vomiting. Later in the course of the illness, fever and leukocytosis are present. Some of the signs used to diagnose appendicitis are tenderness at McBurney’s point and physical findings such as the Rovsing’s, psoas, and obturator signs. The psoas and obturator signs have high specificity for the diagnosis of appendicitis. An iliopsoas muscle strain, however, can cause both to be positive and should be considered as a possible cause of right lower abdominal pain and back pain in a patient without anorexia, fever, nausea, and vomiting.

The location and function of the iliopsoas psoas muscle would cause both the psoas and obturator signs to be positive. The origin of the psoas major is the lateral surface of T12 and L1-4. The psoas muscle joins with the iliacus and inserts at the lesser trochanter of the femur.(Figure 2) Combined, they enable flexion and external rotation at the hip; the motions of both the psoas and obturator signs.

Psoas muscle strains mistaken as appendicitis have been documented in the literature as early as 1913.1 Psoas muscle injury in young athletes has been documented following aggressive training regimens and demonstrated to progress to myositis that presents similarly to appendicitis.2,3 However, any pathologic process within the inguinal region and adjacent areas can lead to a misdiagnosis of appendicitis. Other known causes of positive psoas and obturator signs include hematomas, myositis, bursitis, tendonitis, cysticercosis, and pyomyositis.2,3,4,5,6,7

Acute trauma and overuse resulting from repetitive hip flexion are known major causes of iliopsoas tendinitis. Psoas muscle strains are characterized by relief of pain with rest, pain exacerbation with movement, occurrence in physically active patients, and pain localization at the insertion and origin of the psoas muscle. Treatment consists of ice, rest, anti-inflammatory medications (NSAIDs), and physical therapy for muscle stretching and strengthening.2,6,7 

Discussion: For a patient presenting with right lower quadrant (RLQ) pain, appendicitis is one of the most pressing diagnoses to rule out before moving on to other potential diagnoses. Classically, appendicitis presents with RLQ pain, anorexia, nausea and vomiting. Later in the course of the illness, fever and leukocytosis are present. Some of the signs used to diagnose appendicitis are tenderness at McBurney’s point and physical findings such as the Rovsing’s, psoas, and obturator signs. The psoas and obturator signs have high specificity for the diagnosis of appendicitis. An iliopsoas muscle strain, however, can cause both to be positive and should be considered as a possible cause of right lower abdominal pain and back pain in a patient without anorexia, fever, nausea, and vomiting.

The location and function of the iliopsoas psoas muscle would cause both the psoas and obturator signs to be positive. The origin of the psoas major is the lateral surface of T12 and L1-4. The psoas muscle joins with the iliacus and inserts at the lesser trochanter of the femur. (Figure 2) Combined, they enable flexion and external rotation at the hip; the motions of both the psoas and obturator signs.

Psoas muscle strains mistaken as appendicitis have been documented in the literature as early as 1913.1 Psoas muscle injury in young athletes has been documented following aggressive training regimens and demonstrated to progress to myositis that presents similarly to appendicitis.2,3 However, any pathologic process within the inguinal region and adjacent areas can lead to a misdiagnosis of appendicitis. Other known causes of positive psoas and obturator signs include hematomas, myositis, bursitis, tendonitis, cysticercosis, and pyomyositis.2,3,4,5,6,7

Acute trauma and overuse resulting from repetitive hip flexion are known major causes of iliopsoas tendinitis. Psoas muscle strains are characterized by relief of pain with rest, pain exacerbation with movement, occurrence in physically active patients, and pain localization at the insertion and origin of the psoas muscle. Treatment consists of ice, rest, anti-inflammatory medications (NSAIDs), and physical therapy for muscle stretching and strengthening.2,6,7  

References  

  1. White GR, VII. Contracture of the psoas parvus muscle simulating appendicitis. Ann Surg 1913;58:483-489.
  2. Stabler J. A case of traumatic myositis of the psoas in a gymnast. Injury 1997;28:489-490.
  3. Wysoki MG, Angeid-Backman E, Izes BA. Iliopsoas myositis mimicking appendicitis: MRI diagnosis. Skeletal Radiol 1997;26:316-8.
  4. Graif M, Martinovitz U, Strauss S, et al. Sonographic localization of hematomas in hemophilic patients with positive iliopsoas sign. AJR Am J Roentgenol 1987;148:121-123.
  5. Mittal A, Sharma NS. Psoas muscle cysticercosis presenting as acute appendicitis. J Clin Ultrasound 2008;36:430-431.
  6. Johnston CA, Wiley JP, Lindsay DM, et al. Iliopsoas bursitis and tendinitis. A review. Sports Med 1998;25:271-283.

 

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