Using Radiological Imaging to Differentiate Appendicitis From Fibroids in Gravid Patients

Surgical Rounds®, November 2006, Volume 0, Issue 0

Kerri Buch, Nurse Practitioner, Department of Surgery; Finny George, Medical Student IV, Department of Surgery; Jennifer Conigliaro, Physician Assistant, Department of Surgery; Kaare Weber, Assistant Professor, Department of Surgery; Celia Divino, Associate Professor, Chief, Division of General Surgery, Department of Surgery, Mount Sinai School of Medicine, New York, NY

Kerri Buch, RN, FNP-C

Nurse Practitioner

Department of Surgery

Finny George, BS

Medical Student IV

Department of Surgery

Jennifer Conigliaro, RPA-C

Physician Assistant

Department of Surgery

Kaare Weber, MD

Assistant Professor

Department of Surgery

Celia Divino, MD

Associate Professor

Chief, Division of General Surgery

Department of Surgery

Mount Sinai School of Medicine

New York, NY

Although appendicitis is the most common surgical condition to occur in pregnancy, other conditions, such as symptomatic fibroids, may have a similar presentation. There is considerable debate regarding the safety of using computed tomography scanning to diagnose acute appendicitis during pregnancy. The authors report the cases of two gravid patients suspected of having appendicitis who were found to have uterine fibroid degeneration and torsion on distinct radiological imaging. They also review the incidence of appendicitis during pregnancy, its complications, and the safety and efficacy of radiological testing in gravid women.

The acute abdomen is a difficult presentation in gravid women because of the various physiologic and anatomic changes that occur during pregnancy, the clinicians’ reluctance to obtain radiographic studies, and the surgeons’ hesitancy to operate. Fear of jeopardizing the pregnancy sometimes leads to a conservative wait-and-see approach, which can be fatal.

During pregnancy, appendicitis is the most common cause of abdominal pain requiring emergency surgical treatment.1 Larger series estimate the incidence of acute appendicitis in pregnancy to be between 0.05% and 0.2%, with little variance between trimesters.1,2 Although the maternal mortality rate with appendectomy is almost 0%, it is associated with fetal loss of approximately 2.6% in nonperforated cases and 10.9% in perforated cases.3

Appendicitis during pregnancy can present with signs and symptoms commonly associated with other obstetric problems, such as hemorrhagic luteum cyst, hyperemesis gravidarum, and round ligament pain. There are also many nonobstetric conditions that can mimic acute appendicitis and may require intervention, such as cholecystitis, renal colic, and ovarian torsion. Moreover, symptoms similar to those of acute appendicitis—including nausea, vomiting, abdominal discomfort, anorexia, and leukocytosis—are often found in a normal pregnancy.4 Displacement of the appendix upward by the uterus and increased separation of the visceral and parietal peritoneum further complicate diagnosis.1 Right lower quadrant abdominal pain, an elevated band count, abdominal guarding, and rebound tenderness on palpation may be more specific to acute appendicitis.5

Complications of appendicitis during pregnancy include preterm contractions and preterm labor. A study by Mourad and associates reported these rates in third-trimester patients as 83% and 13%, respectively.6 A third, and most feared, complication is perforation. The rate of perforation in gravid appendicitis patients is approximately 14%, which is higher than that of the general population.2 Perforation can result in a greater incidence of wound infection and peritonitis, and the risks of both increase by trimester.1,6-8 Although complications from an appendectomy can include premature delivery, spontaneous abortion, and stillbirth, surgical intervention must be considered for a pregnant patient whose presentation arouses strong suspicion of appendicitis so that the adverse outcomes of perforation can be prevented.

The overall incidence of fibroids increases as maternal age increases.9 Pregnant patients with symptomatic fibroids often have physical presentations similar to patients with acute appendicitis, making timely and accurate diagnosis difficult. Differentiating these entities is imperative to avoid administering unnecessary general anesthesia to patients with fibroids. Radiological imaging is a vital aid in identifying a surgical emergency.

We describe our experience involving two gravid patients with suspected appendicitis who underwent different modalities of radiological testing. Both patients were determined to be experiencing complications of uterine fibroids and not acute appendicitis. The interpretations of these imaging studies influenced the distinct management of these patients.

Case reports

Case 1 (degenerative fibroid)

—A healthy 33-year-old woman, 25 weeks pregnant and with known fibroids, presented with a 1-week history of progressive, severe right lower quadrant abdominal pain. The patient reported no fevers, chills, nausea, vomiting, or diarrhea. On physical examination, she was afebrile with a gravid abdomen that exhibited marked right and left lower quadrant abdominal tenderness, guarding, and rebound tenderness on palpation.

On admission, the patient’s white blood cell (WBC) count was 15.2 x 103/µL (with a left shift). Ultrasonography failed to identify the appendix and could not exclude acute appendicitis. A computed tomography (CT) scan of the abdomen and pelvis was then performed with oral and rectal contrast and without intravenous contrast, following a low-dose radiation protocol. It revealed a normal appendix and gallbladder, and there was a mixed attenuation fibroid on the right side of the uterus, likely a degenerative fibroid (Figure 1). The patient was treated medically with oral indomethacin, intravenous clindamycin, and gentamycin. She was discharged from the hospital the following day.

Case 2 (torsed fibroid)

— A 40-year-old woman who was 19 weeks pregnant presented to the hospital after experiencing 24 hours of intermittent, sharp right lower quadrant abdominal pain, dysuria, and nausea, but no vomiting. She had a history of nephrolithiasis which had required lithotripsy 7 years earlier. On physical examination, she was afebrile, with right lower quadrant tenderness, guarding, and right costovertebral angle tenderness on palpation. She had normal bowel sounds on auscultation. Her WBC count was 13.2 x 103/µL (with a left shift), and urinalysis was positive for ketones and a small amount of leukocyte esterase but negative for blood.

Because of the radiologist’s hesitancy to perform a CT scan, magnetic resonance imaging (MRI) was used. The MRI revealed an enlarged appendix (9 mm in diameter) with no wall thickening, but there was inflammation in the adjacent fat and a small amount of perihepatic free fluid. It also showed right-sided hydronephrosis and hydroureter and a pedunculated right-sided uterine fibroid (Figure 2).

The patient was taken to the operating room for suspected appendicitis. Laparoscopy revealed a normal appendix; a moderate amount of free fluid in the right lower quadrant and gutter; and a torsed, ischemic fibroid on a stalk. An uncomplicated laparoscopic appendectomy and myomectomy were performed. Pathologic examination demonstrated minimal acute appendicitis. The patient recovered well and was discharged home the following day.

Discussion

Diagnosing acute appendicitis in pregnancy solely by clinical evaluation can be difficult. Transabdominal ultrasonography is fast, safe, and noninvasive and should be the first test performed. Because of ultrasonography’s sensitivity and specificity, its efficacy in diagnosing acute appendicitis in nongravid patients has been reported as more than 90%10; however, a gravid uterus can reposition the appendix, making it difficult to visualize.

Although the increased sensitivity and specificity of CT scanning make it more effective for diagnosing acute appendicitis, with an accuracy rate of up to 98%, clinicians often hesitate to use this modality in pregnant patients for fear of causing fetal injury.11 Typical mean fetal radiation doses have been reported as 8 mGy for abdominal CT scans and 25 mGy for pelvic CT scans.12 This is far below the estimated threshold dose of 200 to 500 mGy at which death, gross malformation, and mental retardation can occur.12 It is also well below the threshold dose of 50 to 110 mGy at which other teratogenic effects can occur, such as decreased intelligence and childhood cancers (particularly leukemia), especially when the fetus is exposed between weeks 10 and 17 of gestation.13 The use of low-dose radiation protocols can result in the delivery of doses even lower than these reported means.

Despite these data, some radiologists are reluctant to perform CT scanning on pregnant patients. In 2000, the International Commission on Radiological Protection recommended that if the dose for the fetus was expected to be high, the clinician should attempt to make a diagnosis without using ionizing radiation.13 MRI is indicated for use in pregnant women when nonionizing diagnostic imaging would be inadequate for making a diagnosis or when MRI is expected to provide important information regarding proper treatment of the fetus or mother.14

MRI can be a valuable tool for evaluating gravid patients with suspected acute appendicitis; however, studies have shown that it enables visualization of a normal appendix in only approximately 90% of nonpregnant patients, a markedly lower percentage than with CT scanning.4,15 Oto and associates retrospectively reviewed the cases of 23 pregnant patients with suspected acute appendicitis who underwent MRI.16 Although this modality correctly identified acute appendicitis in all four patients who actually had the condition, the appendix of one woman who had right lower quadrant inflammation could not be visualized and ovarian torsion was subsequently diagnosed intraoperatively, as was also the case with one of our patients.

A small number of studies did not discover any harmful effects to late-gestation human fetuses that underwent regular MRIs.17-19 Nevertheless, pregnant women should be informed that the safety of MRI during pregnancy has not been proven definitively.14

Both MRI and CT scanning are reasonable options after ultrasonography if appendicitis is suspected in a gravid patient. During the first 17 weeks of gestation, MRI is a safer alternative than CT scanning. After week 17 of gestation, MRI’s lower sensitivity for identifying appendicitis can delay treatment. The risks of radiation-related fetal injury with CT scanning have been demonstrated only with very high doses of radiation; thus, after week 17 of gestation, CT scanning should be the preferred modality secondary to ultrasonography to facilitate the differential diagnosis of appendicitis in pregnant patients.

Conclusion

Acute abdominal pain during pregnancy poses a unique challenge to clinicians. Using the appropriate radiological imaging study to ensure an accurate diagnosis is paramount in managing gravid patients properly and quickly.

Acknowledgment

We would like to thank Emil Cohen, MD, Department of Radiology, Mount Sinai School of Medicine, for providing us with the radiological images.

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