In a patient with prior appendectomy and suspected stump appendicitis, should I order a plain abdominal X‑ray or an ultrasound as the initial imaging study?

Imaging for Suspected Stump Appendicitis

In a patient with prior appendectomy and suspected stump appendicitis, order a CT scan of the abdomen and pelvis with IV contrast as the initial imaging study, not plain X-ray or ultrasound. Plain abdominal radiography has extremely limited diagnostic value for appendiceal pathology and will miss the diagnosis, while ultrasound lacks the sensitivity and field of view needed to reliably detect this rare complication. 1, 2

Why CT is the Definitive Choice

• CT with IV contrast is the gold standard for diagnosing stump appendicitis, demonstrating characteristic findings including the residual appendiceal stump (mean length 3.2 cm), surrounding inflammatory changes, retained appendicoliths (present in 50% of cases), and potential complications such as peristump abscess (29% of cases). 2

• CT achieves 96-100% sensitivity and 93-95% specificity for appendiceal inflammation in adults, far exceeding the performance of plain radiography or ultrasound for this specific clinical scenario. 1, 3

• Stump appendicitis has a characteristic CT appearance that allows confident preoperative diagnosis: the residual stump measures ≥2 cm in most cases, often contains appendicoliths (mean diameter 0.9 cm, mean attenuation 247 HU), and is surrounded by extensive inflammatory changes. 2, 4

Why Plain X-Ray is Inadequate

• Plain abdominal radiography has severely limited diagnostic value for acute appendicitis, with studies showing sensitivity of only 48% and overall accuracy of 67% even for typical appendicitis—far too low to reliably detect the subtle findings of stump appendicitis. 5

• Conventional radiography rarely changes patient management in abdominal pain evaluation and is appropriate only for suspected bowel obstruction, perforated viscus, urinary calculi, or foreign bodies—none of which are the primary concern in suspected stump appendicitis. 1

• The American College of Radiology rates plain radiography as "usually not appropriate" (rating 4 out of 9) for suspected appendicitis, emphasizing its poor diagnostic performance. 1

Why Ultrasound is Insufficient

• Ultrasound has major limitations for detecting stump appendicitis: it is highly operator-dependent, yields equivocal results in 36-68% of adult cases, and has low sensitivity (33.9-51.5%) for detecting complicated appendicitis or perforation. 1, 3

• Non-visualization of the appendix (or stump) on ultrasound does not exclude the diagnosis, and approximately 26% of patients with equivocal ultrasound findings ultimately have appendicitis. 3

• While ultrasound may show some inflammatory changes, it cannot reliably identify the specific features of stump appendicitis (residual stump length, retained appendicoliths, extent of inflammation) that CT demonstrates with high accuracy. 2

Clinical Context of Stump Appendicitis

• Stump appendicitis occurs at a mean interval of 5.1 years after initial appendectomy (range 5 weeks to 17.5 years), with 50% of cases occurring within the first year. 2

• 71% of cases follow laparoscopic appendectomy, where inadequate stump length (≥2 cm residual) and retained appendicoliths predispose to recurrent obstruction and inflammation. 2

• The diagnosis is frequently delayed or missed because clinicians incorrectly assume that prior appendectomy rules out appendiceal pathology, making accurate imaging even more critical. 6

Practical Algorithm

1. Order CT abdomen/pelvis with IV contrast immediately when stump appendicitis is suspected in any patient with prior appendectomy presenting with right lower quadrant pain. 2, 4

2. Do not waste time with plain X-ray or ultrasound first—these modalities will delay definitive diagnosis and potentially worsen outcomes if perforation or abscess develops. 1, 2

3. If CT confirms stump appendicitis, proceed to surgical consultation for completion appendectomy or partial ileocecectomy (50% of cases require open surgical management). 2

4. Initiate broad-spectrum antibiotics covering aerobic gram-negative organisms and anaerobes as soon as the diagnosis is confirmed or strongly suspected. 3

Common Pitfalls to Avoid

• Never assume that a McBurney scar or history of laparoscopic appendectomy rules out appendicitis—this cognitive error leads to diagnostic delay and increased morbidity. 6

• Do not order ultrasound "just to start with something" in this specific clinical scenario—the post-surgical anatomy and need to assess stump length, appendicoliths, and extent of inflammation make CT essential from the outset. 2

• Recognize that stump appendicitis can occur decades after the initial surgery, so even remote appendectomy history does not exclude this diagnosis. 2, 4