With or Without Contrast ?
Hx: A middle aged woman presents with flank pain. She has no past medical history and notes sudden onset of severe, sharp, left flank pain. She denies any history of similar symptoms. Pain is constant, and does not radiate. No associated chest pain, shortness of breath, or abdominal pain. No hematuria, dysuria, hx of kidney stones, change in stools, or blood in the stool. No fever.
- Vitals: HR 100, BP 170/90, sat 100% room air, RR 18
- General: appears to be in significant pain and cannot find a position of comfort.
- HEENT: normal
- Resp: tachypneic, clear to auscultation bilaterally, no wheezes.
- Cardiovascular: tachycardia, regular, no murmurs, pulses normal all extremities
- Abdomen: soft, non-tender,
- Extremities: warm, normal sensation
- Back: pain in left flank without change with movement or palpation.
- Initial differential focused on renal pathology with renal colic at the top of the list.
- kidney / ureteral stones
- renal infract / embolism
- The patient is given narcotic pain medication and blood and urine is obtained.
- Labs are unremarkable and urine is clear.
- A CT urogram is obtained and shows:
- On repeat examination the patient has received little relief with multiple doses of pain medication and has no cause for the severe pain found on CT. The physician is appropriately concerned. The patient has no history of prior visits, narcotic pain medication prescriptions or opiate tolerance, and is still in severe pain. The differential is expanded to include left lower lobe pulmonary embolism and a D-Dimer is ordered.
- The d-dimer returns markedly elevated.
- A CT pulmonary angiogram is ordered and results in the images below:
Diagnosis: Acute Descending (Type B) Aortic Dissection
With or without contrast? A decision that we make routinely when obtaining imaging by computed tomography (CT). With the advancement of this technology, resolution has tremendously improved. Numerous studies have been published regarding the decreasing need for enteric or IV contrast in the emergency setting when imaging the abdomen. These high resolution (64 slice or higher) CT studies are capable of differentiating tissue planes when an adequate amount of intra-abdominal fat is present. This allows for visualization of “infiltration of fat” or edema of the fat surrounding structures like the colon, small bowel, appendix, and retroperitoneal structures like the kidney. The edema becomes a substitute for the hyperemia seen when IV contrast is given and becomes a surrogate marker for inflammation pointing to a pathologic finding. However, even this advanced technology has its limitations. At a time when many departments forgo the administration of contrast in order to facilitate patient flow, it is important to remember the limitations of the non-contrast study.
This case is a good example of several key issues:
- The differential diagnosis: The patient’s presentation appeared classic for a renal colic and she had no risk factors for other disease. The differential was short but did not initially include aortic dissection. Even the expanded secondary differential did not include the process. Flank pain can be caused by dissection. It is generally believed to be associated with involvement of the renal artery. However, this case highlights the possibility of referred pain from dissection of the aorta presenting as flank pain, even in the nascence of renal artery involvement. Though atypical, it should be included in the initial differential. This does not mean it must be excluded by diagnostic testing, but it should be considered.
- The repeat examination: The physician caring for this patient performed one of the most important steps when caring for a patient, the repeat examination. When items on the differential diagnosis have been excluded and no diagnosis has been found, a repeat exam and interview is often helpful. This type of “reset” allows for expansion of a differential, additional historical items to be obtained, and for discovery of new or evolving physical exam findings. Whenever a patient’s response to treatment does not follow the anticipated coarse, or diagnostic testing does not result in an expected diagnosis (both in this case), it is critical to take time to re-evaluate the presentation and overcome any cognitive errors (early closure, etc. ).
- The benefit of contrast: Though CT imaging has come a long way, the identification of vascular abnormalities continues to require the administration of intravenous contrast. As this case highlights, non-contrast imaging of the aorta relies on edema of surrounding structures or aneurysmal dilatation of the aorta to suggest abnormality. In the absence of either of these findings, no further analysis of the aorta can be made. The addition of contrast clearly highlights the intra-vascular space allowing for the correct diagnosis of this life threatening disease.
What do we take away from this case?
- If the differential includes a vascular diagnosis (thrombosis, dissection, embolism) as a likely process, be sure to include the intravenous contrast.
- Be careful not to dismiss the lack of response to treatment.
- Re-examine the patient with a clear mind and a specific focus on expanding your differential if initial testing does not reveal your expected diagnosis and/or treatment is unsuccessful.