Chest computed tomography of a patient revealing severe hypoxia due to amniotic fluid embolism: a case report

Lung iodine mapping images of acute postpartum dyspnea without pulmonary thromboembolism using dual-energy CT

BACKGROUND

Postpartum dyspnea is commonly observed, but its cause is often unknown.

PURPOSE

To investigate postpartum dyspnea, we compared lung iodine mapping (LIM) using dual-energy computed tomography (DECT) between postpartum women and women suspected of having pulmonary thromboembolism (PTE).

MATERIAL AND METHODS

In this retrospective study, 109 women of reproductive age (50 postpartum women, 59 women unrelated to pregnancy) underwent DECT between March 2009 and August 2020. Among the postpartum women, 23 patients were excluded due to late-onset dyspnea (n=20: >48 h after delivery) or the presence of PTE (n=3). A total of 86 patients were divided into three groups (27 postpartum women [postpartum group], 19 women with PTE [PTE group], and 40 women without PTE [non-PTE group]). Quantitation was applied to a decreased LIM value (LIM5; defined as <5 HU) and the relative value of LIM5 to whole LIM volume (%LIM5). LIM defects were classified into five patterns (0 = none, 1 = wedge-shaped, 2 = reticular/liner, 3 = diffuse granular/patchy, 4 = massive defects) based on a consensus between two readers.

RESULTS

There were significant differences in the LIM5 and %LIM5 values among the three groups. The LIM5 and %LIM5 were largest in the PTE group, and postpartum women showed intermediate values between the non-PTE and PTE groups. Wedge-shaped defects were prominent in the PTE group, and diffuse granular/patchy defect was a typical feature in the postpartum group.

CONCLUSION

Postpartum women with dyspnea showed granular/patchy defects on DECT with a median quantitative value between the PTE and non-PTE groups.

A Pictorial Review of Postpartum Complications

The postpartum period, also known as the puerperium, begins immediately after delivery of the neonate and placenta and ends 6-8 weeks after delivery. The appearance of physiologic uterine changes during puerperium can overlap with that of postpartum complications, which makes imaging interpretation and diagnosis difficult. Obstetric and nonobstetric postpartum complications are a considerable source of morbidity and mortality in women of reproductive age, and the radiologist plays an important role in the assessment of these entities, which often require a multimodality imaging approach. US and contrast material-enhanced CT are the techniques of choice in the emergency department, and they can show characteristic radiologic findings that enable differentiation between normal and abnormal features to help radiologists and emergency department practitioners to reach a correct diagnosis and provide timely treatment. The spectrum of postpartum complications ranges from relatively self-limiting to life-threatening conditions that can be divided into six categories: infectious conditions (endometritis), thrombotic complications (eg, deep vein thrombosis, ovarian vein thrombophlebitis, HELLP [hemolysis, elevated liver enzymes, and low platelet count] syndrome, or cerebral sinus thrombosis), hemorrhagic conditions (eg, uterine atony, trauma of the lower portion of the genital tract, retained products of conception, uterine artery arteriovenous malformations, or uterine artery pseudoaneurysm), cesarean delivery-related complications (eg, bladder flap hematoma, subfascial hematoma, rectus sheath hematoma, abscess formation, uterine dehiscence, uterine rupture, vesicovaginal fistula, or abdominal wall endometriosis), iatrogenic conditions (eg, uterine perforation), and nonobstetric complications (eg, acute cholecystitis, acute appendicitis, uterine fibroid degeneration, renal cortical necrosis, pyelonephritis, posterior reversible encephalopathy syndrome, or pituitary gland apoplexy). The online slide presentation from the RSNA Annual Meeting is available for this article. ^©RSNA, 2020.

Beyond Pulmonary Embolism; Nonthrombotic Pulmonary Embolism as Diagnostic Challenges

Nonthrombotic pulmonary embolism (NTPE) is less well understood and is encountered less frequently than pulmonary embolism from venous thrombosis. NTPE results from embolization of nonthrombotic material to the pulmonary vasculature originating from many different cell types as well as nonbiologic or foreign materials. For many radiologists NTPE is a challenging diagnosis, presenting nonspecific or unusual imaging findings in the setting of few or unusual clinical signs. The aim of this paper is to review the pathophysiology of diverse causes of NTPE, which should aid radiologists to better understand and, more importantly, diagnose these infrequent events.

Imaging of Pulmonary Embolus: Thrombotic, Nonthrombotic, and Mimickers

Pulmonary embolism is a common and potentially fatal pathological condition. Imaging plays a crucial role in the diagnosis and differentiation of the causes of pulmonary embolus. Here we present typical imaging findings associated with both thrombotic and nonthrombotic pulmonary emboli, as well as their potential mimickers.

[Nonthrombotic pulmonary embolisms]

The term nonthrombotic pulmonary embolism (NTPE) is defined as embolization of pulmonary arteries caused by foreign bodies (e. g. detached catheter fragments), biological substances (e. g. septic thrombus) or exogenous substances (e. g. gas). The frequency of NTPE is underestimated. Symptoms can cover the spectrum from undetectable to sudden death. In addition to mechanical obstruction of the pulmonary arteries, some NTPEs trigger an inflammatory cascade that causes deterioration of vascular, pulmonary and cardiac function. Radiological imaging in combination with the medical history of patients is sufficient to identify most NTPEs with certainty. The aim of this article is to make readers aware of the symptoms, frequency, relevance, classification, pathophysiology, laboratory findings and radiological findings of the most frequent forms of NTPE. The spectrum of forms presented here includes pulmonary embolisms due to foreign bodies (intravascular, intracorporeal and extracorporeal), amniotic fluid, endogenous tissue, fat, tumors, septic thrombi, hydatids, cement, metallic mercury, gas, silicone and particles.