"A dilated ureter caused by physiologic hydronephrosis, and a dilated ovarian vein, may both mimic a dilated appendix, but the former two can be followed for a longer distance within the retroperitoneum, and the signal changes on SSFSE and gradient-echo sequences will enable these structures to be differentiated. On gradient-echo images, the ureter and ovarian vein will have a high signal and lie close to each other anterior to the psoas, whereas on SSFSE images, the ureter maintains a high signal but the ovarian vein will have flow voids within."
"A dilated ureter caused by physiologic hydronephrosis, and a dilated ovarian vein, may both mimic a dilated appendix, but the former two can be followed for a longer distance within the retroperitoneum, and the signal changes on SSFSE and gradient-echo sequences will enable these structures to be differentiated. On gradient-echo images, the ureter and ovarian vein will have a high signal and lie close to each other anterior to the psoas, whereas on SSFSE images, the ureter maintains a high signal but the ovarian vein will have flow voids within."
Expected headings
"MRI protocol"
"Bowel diseases"
"Acute appendicitis"
"Crohn disease"
"Bowel obstruction"
"Hepatobiliary diseases"
"Cholelithiasis, choledocholithiasis, cholecystitis and pancreatitis"
"Urogenital diseases"
"Pyelonephritis"
"Ureteric stones"
"Adrenal infarction"
"Gynaecologic diseases"
"Degenerating fibroids"
"Ectopic or heterotopic pregnancy"
"Ovarian torsion"
"Ovarian hyperstimulation syndrome"
"Obstetric diseases"
"Vascular diseases"
"Acute non-traumatic abdominal pain in pregnancy requires a considered imaging approach due to the increased risks of fetal demise associated with undiagnosed diseases such as perforated acute appendicitis. Ultrasound is the first-line modality due to its wide availability and ability to diagnose a range of abdominal diseases. However, due to changes in the location of organs caused by displacement by the gravid uterus, identification of structures such as the appendix may not be possible, and as such MRI has gained a growing role in this setting. MRI has been shown to have a high sensitivity, specificity and positive predictive value for the diagnosis of acute appendicitis in pregnancy 12,13."
"An MRI protocol for assessing non-traumatic abdominal pain in pregnancy encompasses sequences that allow for assessment of bowel, solid organs, ovaries and uterus, although not for detailed examination of the fetus."
"Cholelithiasis, choledocholithiasis, cholecystitis and pancreatitis"
"There is an increased risk of venous thromboembolism in pregnancy, and the adrenal glands can undergo acute non-haemorrhagic infarction due to venous thrombosis. On MRI, there is oedema, thickening and lengthening of the adrenal gland limbs, with oedema of the surrounding fat 6."
"Ovarian torsion is seen most frequently in the first trimester, thought to be due to rapid enlargement of the uterus leading to increased mobility of the broad ligament and vascular pedicles of the ovaries. Torsion may occur secondary to an ovarian mass, which may be a benign follicular cyst or a malignant lesion such as a cystadenoma or dermoid cyst. Features on imaging include ovarian enlargement, oedema and surrounding fluid. The uterus may be displaced away."
"Acute appendicitis in pregnancy occurs at a similar frequency as outside of pregnancy, and is the most common reason for emergency non-obstetric surgery in pregnancy. There is an increased risk of fetal demise with complications of acute appendicitis such as perforation, and there are also risks associated with anaesthesia and increased rates of fetal loss with negative appendicectomies, underlining the importance of prompt and accurate imaging 9."
"There is an increased rate of gallstone formation in pregnancy, and therefore a significant proportion of women will present with various facets of gallstone disease. The imaging features on ultrasound and MRI are identical to those outside of pregnancy, and due to the epigastric location, there is little change to the expected findings by the gravid uterus."
"There is an increased risk of venous thromboembolism in pregnancy, and the adrenal glands can undergo acute non-haemorrhagic infarction due to venous thrombosis. On MRI, there is oedema, thickening and lengthening of the adrenal gland limbs, with oedema of the surrounding fat 6."
"There is an increased rate of thrombosis in pregnancy, and most thromboses are readily detected using ultrasound. MRI may be helpful in areas not accessible by ultrasound, such as the ovarian veins. A lack of a flow void on T2 weighted images (i.e. the normal low signal void is not present and instead there is high signal) or low signal on gradient-echo images are key signs."
"Physiologic hydronephrosis is commonly seen in pregnancy, caused by a combination of hormone-mediated smooth muscle relaxation and physical compression of the ureters between the uterus and psoas muscles. The ureter will be seen to taper smoothly in these cases. If a standing column of urine ends above or below the level of the sacral promontory, a ureteric stone should be looked for carefully; a low-signal intraluminal structure may be identified."