Intern Ultrasound of the Month: AAA & Ureteral Compression
The Case
71 yo male with PMH including hypertension, hyperlipidemia, diabetes, asthma, COPD, dementia, BPH, schizophrenia presented to the emergency department from his skilled nursing facility for “weakness” and flank pain. Also reported dysuria and had poor PO intake. Patient was somewhat confused and not providing the most reliable history.
Initial vitals were within normal limits. On exam, he was tired-appearing but in no acute distress. His exam was significant for bilateral CVA tenderness. His abdominal exam was unremarkable and no apparent focal neurovascular deficits were noted.
Labs were significant for acute kidney injury with BUN of 50 and creatinine 2.9. Otherwise stable. Urinalysis was normal.
Point-of-care ultrasound of aorta and kidneys revealed the following:
Enlarged aorta with intramural thrombus
Bidirectional flow seen within the patent lumen, surrounded by thrombus
POCUS findings collectively consistent with AAA with suspected secondary ureteral compression causing hydronephrosis.
FAST exam was negative & no other signs of rupture seen.
Measured 5 x 5.5 cm
Right kidney with hydronephrosis (Left kidney was normal-appearing)
Case continued: CT abdomen/pelvis was obtained, confirming unruptured AAA (apparently previously diagnosed but now with an interval increase from prior imaging), along with right-sided hydronephrosis from ureteral compression. Vascular surgery was consulted, and elective repair of the AAA was felt to be in the patient’s best interest. He was admitted to medicine, AKI improved with fluids, and his hospital course was complicated primarily by delirium without any further issues related to his AAA.
Abdominal Aortic Aneurysm (AAA)
BACKGROUND
Found in 8% of men over the age of 65 yrs [1]
Risk factors include older age, male gender, smoking, hypertension, atherosclerotic disease
Size correlates with risk of rupture (increased risk >5.5cm). Mortality of rupture exceeds 80% [2]
Majority are infra-renal but can occur anywhere along the aorta (& iliac arteries)
Clinical Presentation
Majority are asymptomatic until rupture occurs. May have abdominal/flank/back pain. Can mimic renal colic.
Only 61% of patients present with classic triad of abdominal pain, hypotension, pulsatile mass [3]
Management — per ACC/AHA 2005 Practice Guidelines [4].
Emergent surgery if rupture or hemodynamically unstable
Surgical management indicated if >5.5 cm (even if asymptomatic), rapidly expanding, or symptomatic (regardless of size)
If asymptomatic & <5.5 cm —> medical management, observation
Consider CT for stable patients
Direct compression of surround structures (such as ureters) is one of the complications
Ureteral obstruction thought to occur in 20-30% of inflammatory aortic aneurysms, most often due to fibrosis surrounding the aneurysm [5]
Aorta POCUS
Technique [6]
Curvilinear probe is best
Look for vertebral shadow.. IVC will lie to pt right of the aorta.
Place probe in transverse orientation with probe marker pointing toward patient right
Scan from epigastrium down to the bifurcation to right and left common iliac arteries. Visualize the aorta in its entirety.
Include proximal, mid, distal aorta, bifurcation including iliac vessels
Also view in long axis (probe marker toward head) to ensure you don't miss focal (saccular) aneurysms
Evaluate for:
Size/ diameter (measure outer wall to outer wall)
Aorta >3 cm & iliac > 1.5 cm are considered aneurysmal
Turbulent/bidirectional flow (yin yang or Pepsi sign)
Intramural thrombus
Echogenic material in a normally anechoic lumen; associated with weaker walls & earlier rupture. May result in a false negative measurement if not measuring outer wall to outer wall
Signs of rupture
Hemoperitoneum, retroperitoneal hematoma, displaced kidney, aortic wall disruption, etc. [7]
Pearls & Pitfalls
Confirm that you are measuring aorta, not IVC. If not obvious visually, use doppler (color, pulse wave) to help
Measure outer wall to outer wall at the widest visualized part of the vessel to ensure accurate measurement
Have pt flex hips/knees to relax abdominal muscles
Use graded compression to help displace bowel gas. Also, lateral decubitus positioning and hepatic window if still having difficulty with visualization
Perform FAST exam to evaluate for rupture. But know that bleeding might be localized to the retroperitoneum, which is more difficult to see on POCUS.
The Evidence
Sensitivity 99%, specificity 98% for emergency department POCUS in diagnosing suspected AAA [8]
While CTA may be the gold standard, POCUS allows for faster time to diagnosis with improved mortality rate compared to radiology study [9]
Take Home Points
Have a low threshold to evaluate the aorta with POCUS in patients with abdominal, flank, back pain, especially if elderly and/or unstable
Completely visualize the aorta in both longitudinal and transverse views & measure outer wall to outer wall
Not all hydronephrosis is from a kidney stone or other intrinsic urinary tract pathology
POST BY: DR. CAMERON CRANDALL, PGY1
FACULTY EDITING BY: DR. LAUREN MCCAFFERTY
References
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Kent KC. Clinical practice. Abdominal aortic aneurysms. N Engl J Med. 2014; 371(22):2101–8.
Azhar B, Patel SR, Holt PJ, et al. Misdiagnosis of ruptured abdominal aortic aneurysm: systematic review and meta-analysis. J Endovasc Ther. 2014; 21:568-75.
Hirsch AT, Haskal ZJ, Hertzer NR. ACC/AHA 2005 Practice Guidelines. Circulation. 2006;113:e463–e654.
Galosi AB, Cicilioni CG, Sbrollini G, Angelini A, Maselli G, Carbonari L. Inflammatory abdominal aortic aneurysm presenting as bilateral hydroureteronephrosis: A case report and review of literature. Arch Ital Urol Androl. 2014; 86 (4): 385-386.
Noble V, Nelson B. (2011). Abdominal aorta ultrasound. In Manual of Emergency and Critical Care Ultrasound (pp. 115-132). Cambridge: Cambridge University Press.
Catalano O, Siani A. Ruptured abdominal aortic aneurysm. Categorization of sonographic findings and report of 3 new signs. J Ultrasound Med. 2005;24(8):1077–1083.
Rubano E, Mehta N, Caputo W, Paladino L, Sinert R. Systematic review: emergency department bedside ultrasonography for diagnosing suspected abdominal aortic aneurysm. Acad Emerg Med. 2013; 2:128-38.
Plummer D, Clinton J, Matthew B. Emergency department ultrasound improves time to diagnosis and survival in ruptured abdominal aortic aneurysm.” Acad Emerg Med. 1998. 5:417