Case 24: Diverticulitis

 

A 56 year old male with a history of uncomplicated diverticulitis presented to the emergency room with left lower quadrant pain and loose stools for the last six days. He denies fever, vomiting or blood in hist stool 

Vitals: T 97.3   BP 152/81   HR 91       RR 18      SPO2 97% on RA

 

You physical exam shows tenderness to palpation in the left lower quadrant with no peritoneal signs. You are on the fence about getting a CT abdomen and pelvis with contrast to look for an abscess versus treating this as uncomplicated diverticulitis. You decide to throw the ultrasound probe on the area of his pain. What do we see in these images? How would this change management?

 

Answer and Learning Points

Answer:

The three videos and two images show diverticulitis with an abscess or phlegmon beneath the bowel loops. Though CT is the gold standard for diagnosing diverticulitis, ultrasound is relatively sensitive in the diagnosis and has the advantage of being cheap, fast and radiation-free (1). 

When looking for diverticulitis on ultrasound physicians will typically use a "lawn mower" approach to the left abdomen to search for areas of affected bowel. One way to get to the area of interest more quickly is simply ask the patient to point to the area of maximal tenderness and start there, similar to appendicitis or small bowel obstruction. There are a few findings on ultrasound that indicate diverticulitis (2,3):

  1. Thickening of bowel wall, typically at least 4-5mm
  2. Echogenic fat surrounding the bowel, which is representative of fat stranding seen on CT
  3. Diverticulum
diverticulitis ultrasound
Wall thickening and fat stranding

 

Ultrasound is also helpful in looking for abscess, such as in our case. We see there is an area of hypoechogenicity with no color flow, representing likely abscess adjacent to the bowel.  

 

Our patient ultimately got a CT scan that confirmed he had diverticulitis with abscess. He was admitted to medicine with GI and surgery consults following.

References

(1) Lameris, W et al. Graded compression ultrasonography and computed tomography in acute colonic diverticulitis: meta-analysis of test accuracy. Eur Radiol. 2008 Nov;18(11):2498-511.

(2) Schwerk, WB et al. Sonography in acute colonic diverticulitis. A prospective stud. Dis Colon Rectum. 1992 Nov;35(11):1077-8

(3) Mazzei M et al. Sigmoid diverticulitis: US findings. Crit Ultrasound J. 2013 Jul 15;5 Suppl 1(Suppl 1):S5.

This post was written by Charles Murchison MD, with editing from Colleen Campbell MD and Amir Aminlari MD.

Case # 3: Under Your Skin

A 52 year old male with presents with 4 days of painful swelling and redness to his middle right thigh. Physical exam shows a 3 cm area of erythema that is tender to touch. He denies fever and trauma to the area. A bedside ultrasound is performed as seen below. What is the next step in management?

Vitals: HR 82 BP 110/72 RR 14 O2 98

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Answer and Learning Point

Answer

Incision and drainage. The image above demonstrates a well circumscribed fluid collection within the soft tissue,  without evidence of surrounding cellulitis. The above abscess was incised with immediate release of a large volume of purulent material. The patient did well.

Learning Point

    • Ultrasound is an excellent adjunct to the physical exam in the evaluation of soft tissue infections. It improves accuracy in the diagnosis of superficial abscesses and has been shown to change management in up to 50% of emergency department cases of clinical cellulitis [1,2].
    • The ultrasound image above is atypical for an abscess given the iso-echoic texture appreciated in the fluid and is easily missed if the operator is not aware of this unusual finding. Most abscesses will appear as a hypoechoic fluid collection, however occasionally they may have increased internal echoes which can lead to false negative ultrasound results.
    • This can be avoided by applying gentle pressure to the area of the suspected cellulitis/abscess to evaluate for the "swirl sign" which is indicative of fluid movement within the abscess cavity [Figures 1&2].
    • This can be distinguished from the common pattern appreciated in cellulitis known as "cobblestoning" which indicates increased subcutaneous fluid.
Figure 1: Soft tissue ultrasound demonstrating swirling of iso-echoic fluid collection consistent with abscess. Image courtesy of UOTW.
Figure 2: Additional soft tissue ultrasound demonstrating the "swirl sign." Image courtesy of UOTW.

References

 Tayal VS, e. (2017). The effect of soft-tissue ultrasound on the management of cellulitis in the emergency department.

Squire BT, e. (2017). ABSCESS: applied bedside sonography for convenient evaluation of superficial soft tissue infections.

UOTW: Case 66