Complicated acute appendicitis in pregnancy (MRI)

Case contributed by Dr Vikas Shah

Presentation

26/40 pregnant. Lower abdominal pain and fever.

Patient Data

Age: 35 years
Gender: Female
MRI

Initial MRI

Intrauterine pregnancy confirmed but not interrogated in detail. An inflammatory process is present in the right lower quadrant, extending into the deep pelvis. Air-fluid levels are seen within several pockets within the rectovaginal space. Extending from the cecal pole and inferiorly and medially is an elongated tubular structure with both low and high signal within on SSFSE and gradient echo images, and high signal on the T1 water-only images. This may indicate blood. The right ovary lies anterior to this. 

The appearances are highly concerning for a luminal perforation, most likely from a grossly enlarged and inflamed appendix, although it is not clear why there would be blood in this region.

Histopathology

Clinical History: Limited right hemicolectomy for ? appendiceal carcinoid, ? appendicitis.

Macroscopic: Partial right hemicolectomy measuring 130 x 90mm. The attached terminal ileum measures 40 x 15 x 5mm. The appendix is grossly distorted and measures 75 x 35mm. The appendix appears haemorrhagic. Upon slicing the distal end of the appendix contains a faecolith. The appendix and attached meso-appendix appears haemorrhagic. No obvious mucous is seen within the lumen.

Microscopic: The sections taken from the appendix show evidence of extensive decidualised endometriosis. There is focal evidence of acute appendicitis with occasional microabscesses within the wall of the appendix. There is no evidence of low grade appendiceal mucinous neoplasm or goblet cell carcinoid in the multiple sections examined from the appendix. The appearances are those of appendiceal endometriosis with decidualisation secondary to the ongoing pregnancy. Four lymph nodes have been retrieved from this specimen, of which three are involved by foci of decidualised stroma.

Conclusion: Limited right hemicolectomy - acute appendicitis and extensive decidualised endometriosis. Three out of four lymph nodes involved by endometriosis. No evidence of dysplasia or malignancy.

MRI

Repeat MRI 4 weeks after surgery, at 30/40 gestation, for persisting pyrexia

Intrauterine pregnancy confirmed but not interrogated in detail. There are multiple pockets of fluid within the deep pelvis, as well as a 10 cm thick-walled collection in the right lower quadrant, confirming the presence of intra-abdominal abscesses. The large abscess compresses the right ureter against te right psoas muscle, mimicking the physiologic hydronephrosis of pregnancy usually caused by the gravid uterus causing this compression.

Case Discussion

In retrospect, the signal changes and anatomic findings can be explained by the results from the pathology analysis; the grossly enlarged tubular structure posterior to the right ovary and closely related to the cecal pole, containing heterogeneous signal, is the hemorrhagic appendix with changes of endometriosis within. Perforation has occurred as shown by the pockets with air-fluid levels. 

This study also demonstrates the utility of MRI for post-operative assessment in pregnancy in order to reduce the radiation burden imposed by CT. The follow up study shows a large abscess in the right lower quadrant as well as several smaller collections in the deep pelvis. The large abscess compresses the right ureter against the right psoas muscle, mimicking the physiologic hydronephrosis of pregnancy usually caused by the gravid uterus causing this compression. 

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Case information

rID: 87391
Published: 24th Mar 2021
Last edited: 18th Jul 2021
Inclusion in quiz mode: Included

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