Lymphatic flow and anatomy can be challenging to study, owing to variable lymphatic anatomy in patients with diverse primary or secondary lymphatic pathologic conditions and the fact that lymphatic imaging is rarely performed in healthy individuals. The primary components of the lymphatic system outside the head and neck are the peripheral, retroperitoneal, mesenteric, hepatic, and pulmonary lymphatic systems and the thoracic duct. Multiple techniques have been developed for imaging components of the lymphatic system over the past century, with trade-offs in spatial, temporal, and contrast resolution; invasiveness; exposure to ionizing radiation; and the ability to obtain information on dynamic lymphatic flow. More recently, dynamic contrast-enhanced (DCE) MR lymphangiography (MRL) has emerged as a valuable tool for imaging both lymphatic flow and anatomy in a variety of congenital and acquired primary or secondary lymphatic disorders. The authors provide a brief overview of lymphatic physiology, anatomy, and imaging techniques. Next, an overview of DCE MRL and the development of an MRL practice and workflow in a hybrid interventional MRI suite incorporating cart-based in-room US is provided, with an emphasis on multidisciplinary collaboration. The spectrum of congenital and acquired lymphatic disorders encountered early in an MRL practice is provided, with emphasis on the diversity of imaging findings and how DCE MRL can aid in diagnosis and treatment of these patients. Methods such as DCE MRL for assessing the hepatic and mesenteric lymphatic systems and emerging technologies that may further expand DCE MRL use such as three-dimensional printing are introduced. ^©RSNA, 2024 Test Your Knowledge questions for this article are available in the supplemental material.

BACKGROUND Severity of emergency general surgery (EGS) diseases has not been standardized until recently. The American Association for the Surgery of Trauma (AAST) proposed an anatomic severity grading system for EGS diseases to facilitate communication and quality comparisons between providers and hospitals. Previous work has demonstrated validity of the system for appendicitis in the United States. To demonstrate generalizability, we aim to externally validate this grading system in South African patients with appendicitis. METHODS Patients with acute appendicitis during 2010 to 2016 were identified at multi-institutional sites within South Africa. Baseline demographics and procedure types were recorded, and AAST grades were assigned based on intraoperative findings. Outcomes included duration of stay, mortality, and Clavien-Dindo complications. Summary statistical univariate and nominal logistic regression analyses were performed to compare AAST grade and outcomes. RESULTS A total of 1,415 patients with a median (interquartile range) age of 19 years (14–28 years) were included (55% men). One hundred percent underwent appendectomy: 63.5% completed via midline laparotomy, 36.5% via limited incision (31.8% via McBurney incision and 4.7% via laparoscopy). Overall, 30-day mortality rate was 1.4% with an overall complication rate of 44%. Most common complications included surgical site infection (n = 147, 10.4%), pneumonia (n = 105, 7.4%), and renal failure (n = 64, 4.5%). Distribution of AAST grade is as follows: Grade 0 (10, 0.7%), Grade 1 (247, 17.4%), Grade 2 (280, 19.8%), Grade 3 (158, 11.3%), Grade 4 (179, 12.6%), and Grade 5 (541, 38.2%). Increased median (interquartile range) AAST grades were recorded in patients with complications, 5 (3–5) compared with those without (2 [1–3], p = 0.001). Duration of stay was increased for patients with higher AAST grades: 4 and 5 (10.6 ± 5.9 days) versus I and II (3.6 ± 4.3 days; p = 0.001). Area under the receiver operating characteristic analysis to predict presence of any complication based on AAST grade was 0.90. CONCLUSION The AAST EGS grading system is valid to predict important clinical outcomes in a South African population with an increased degree of severity on presentation. These results support generalizability of the AAST EGS grading system for appendicitis in a developing nation. LEVEL OF EVIDENCE Prognostic, level II.