Role of Ultrasound in the Assessment and Differential Diagnosis of Pelvic Pain in Pregnancy

Abstract

Pelvic pain (PP) is common in pregnant women and can be caused by several diseases, including obstetrics, gynaecological, gastrointestinal, genitourinary, and vascular disorders. Timely and accurate diagnosis as well as prompt treatment are crucial for the well-being of the mother and foetus. However, these are very challenging. It should be considered that the physiological changes occurring during pregnancy may confuse the diagnosis. In this setting, ultrasound (US) represents the first-line imaging technique since it is readily and widely available and does not use ionizing radiations. In some cases, US may be conclusive for the diagnosis (e.g., if it detects no foetal cardiac activity in suspected spontaneous abortion; if it shows an extrauterine gestational sac in suspected ectopic pregnancy; or if it reveals a dilated, aperistaltic, and blind-ending tubular structure arising from the cecum in suspicious of acute appendicitis). Magnetic resonance imaging (MRI), overcoming some limits of US, represents the second-line imaging technique when an US is negative or inconclusive, to detect the cause of bowel obstruction, or to characterize adnexal masses.

Keywords: emergency; gastrointestinal tract; gynaecology; magnetic resonance; obstetrics; urinary system; vascular system.

Figure 1

36 y.o. woman with pelvic pain and vaginal bleeding during the first trimester. (A,B) Convex probe axial and longitudinal scans of uterus show the presence of abnormal uterine shape for inhomogeneous content of cavity without concomitant visualisation of an embryo; the foetal cardiac activity was not detectable. (C,D) T2 FSE and TS fat-sat axial images of enlarged uterus confirm the altered content of cavity with no recognisable fetus.

Figure 2

27 y.o woman with vaginal bleeding and pelvic pain. (A) US examination shows an inhomogeneous mass (“blob sign”) morphologically similar to a gestational sac in the right ovary; (B) cardiac activity is detected on power doppler; (C) free fluid is also present at the hepato-renal interface.

Figure 3

B-mode US scan (A) and T1 LAVA (B) and T2 FSE (C) coronal images of a pregnant woman. (A) US reveals a severe change of placental structure with inhomogeneous placental thickening. (B,C) MRI sequences show the separation of the placenta from the myometrium in the uterus due to blood accumulation and compression on the uterine wall away from the placenta; a subchorionic hematoma (localised between the chorionic membrane and uterine wall) is diagnosed.

Figure 4

(A) Pelvic US scan of free inhomogeneous fluid in the pouch of Douglas compatible with hemoperitoneum; the uterus is enlarged and inhomogeneous with apparent wall defect. (B,C) CT axial images of the same patient show conspicuous hemoperitoneum; the gravid uterus is characterized by a severe thickness wall reduction (red circle), which corresponds to uterine tear. (D) CT coronal post-processed image (MIP) in venous phase clarifies the uterine vascularization and bleeding site.

Figure 5

US B-mode scans. (A) Large solid leiomyoma of the uterus with inhomogeneous internal echotexture, (B) some vascular spots at power Doppler.

Figure 6

US B-mode scans in a pregnant woman during the third trimester. (A) Axial image of the right kidney shows a regular cortical-medullary pattern and physiological dilatation of renal pelvis; (B) also the lumbar tract of the right ureter is dilated. (C) Exploration of pelvis detects increase in size of the uterus with compression effect on the surrounding structures.

Figure 7

Spectral Doppler and Colour Doppler scans of the right kidney in a pregnant woman with urinary obstruction. Presence of moderate hydronephrosis without the US detection of a calculus; (A) the resistivity index is normal, (B) while the venous impedance index is increased.

Figure 8

US B-mode (A,B) and Colour Doppler (C) scans in pregnant woman with right flank pain and nausea. (A) Collecting system of the right kidney is dilated with evidence (B) of a calculus (arrow) in the middle tract of the lumbar ureter resulting in complete urinary obstruction and mild hydronephrosis; (C) no right ureteral jet is detected on Colour-Doppler.

Figure 9

Spectral (A,B) and Color (C,D) Doppler scans of the right kidney and bladder in a pregnant woman with right flank and pelvic pain in incomplete urinary obstruction. (A) Mild hydronephrosis with no notable obstructive calculus is detected and the resistivity index is slightly increased on spectral Doppler (A) as well as the venous impedance index (B). (C,D) The ureteral jet is reduced on the right compared to the left side.

Figure 10

US B-mode scans in a pregnant woman arrived in the ER presenting fever and dysuria associated with right flank and pelvic pain. (A) A longitudinal image of hepato-renal scan shows thickened wall of right renal pelvis due to inflammation; (B) in the pelvis the foetus within the gravid uterus is demonstrated.

Figure 11

(A) US B-mode scan in a pregnant woman diagnosed with pyelonephritis and moderate dilatation of the right renal pelvis. Contrast-enhanced CT axial (B), coronal (C), and sagittal (D) images in the venous phase of the same patient after delivery. The right kidney appears slightly enlarged than the left one with persistent pelvis dilatation; some focal wedge-like regions of reduced enhancement are detected, confirming the presence of peri-partum pyelonephritis.

Figure 12

US B-mode (A) and Colour Doppler (B) scans of a pregnant woman with right iliac fossa pain. Acute appendicitis appears as aperistaltic, non-compressible and blind-ending tubular structure with thickened walls arising from the cecum. The surrounding fat is hyperechoic and inflamed. The color Doppler reveals an increased vascular flow of the appendix walls due to inflammation.

Figure 13

US and CT examinations of a pregnant woman who suffered from left pelvic pain before delivery. US B-mode scans of the left ovarian vein in axial (A) and longitudinal (B) views before delivery show the ovarian vein as a tubular structure with heterogeneous hypoechoic echotexture, located superiorly to the ovary and anteriorly to the psoas muscle. (C) Contrast-enhanced CT coronal image was performed after delivery and confirmed the left gonadic vein thrombosis (red circle).