Radiology Part 2: Acute Abdomen Radiology Case Studies With Dr. Ty Vachon

EBP Guidelines, Gastrointestinal, Interview, Podcast, Radiology 3

The Nurse Practitioner Show Podcast Episode 21 - Radiology Part 2: Abdominal Radiographic Case Studies with Radiologist and Imaging Informaticist Dr Ty Vachon, MD | Guest Hosted by Dr. Cynthia Jaffe, Chiropractor Family Nurse Practitioner | Dr Rachel Danford Silva NP

Click play above to hear episode 21 of The Nurse Practitioner Show Podcast™

Acute Abdominal Case Studies

Clinical Questions To Consider

Two major clinical questions to answer when considering case studies to be discussed:

  1. What is the differential diagnosis?
  2. What information is necessary to make a definitive management decision?

When ordering radiographic images in patients with acute abdominal symptoms, it is helpful to the radiologist to have relevant information regarding the patient’s age and posture-are they guarding their abdomen or are they doubled over in pain- as well as lab values and the diagnosis/differential diagnosis.

First Clinical Scenario

75 year old female patient with intermittent lower left quadrant abdominal pain. Patient states she has not eaten anything unusual in her diet and has a healthy diet including fruits and vegetables. The patient started eating sunflower seeds daily every evening in her salads.

We can distinguish diverticulosis without diverticulitis. If we see outpouchings from the colon that has no inflammation around it, it is known as diverticulosis. If one of the sunflower seeds gets stuck in a pouch, it can become inflamed or infected and is now called diverticulitis. This will result in fever with increased WBC counts.

A contributing factor to diverticulosis is a low-fiber diet, a chronic problem within the american diet. Without fiber to add bulk to the stool, the colon has to work harder than normal for peristalsis to move the stool forward. The differential pressure from this may actually cause pouches to form in the weak spots along the colon.

Diverticulitis symptoms are typically left lower abdominal pain

In a first time patient with diverticulitis, the initial radiology exam should be CT of the abdomen with oral contrast. On the ordering form for the radiographic image, state concern of diverticulitis to alert the radiologist of specific concern. The sensitivity of an abdominal CT with oral contrast for diverticulitis is high.

Presentation Not Clear? 

If the patient’s presentation of acute abdominal onset is not clear, a supine or upright x-ray can show bowel obstruction, as well as renal calculi (kidney stones). Once the radiographic image indicates an obstruction, preparation for abdominal surgery must be made. Free air can be visualized under the domes of the diaphragm. in addition, a high stool burden can be visualized to correlate with constipation.

Many institutions and emergency departments utilize x-ray images in patients with acute abdominal pain. X-ray images are widely available, easily performed, and used by providers to exclude major illnesses, such as bowel obstruction or perforated viscus.

Other Considerations:
  1. Older diabetic patient with renal disease and abdominal pain, CT without contrast is preferred.
  2. Patients 30 years of age and younger are more sensitive to radiation; therefore, when possible consider MRI imaging rather than CT scans to avoid radiation exposure, when possible.
  3. In pregnant patients with abdominal pain attempt an ultrasound first, before an MRI. Keep in mind flank pain may indicate hydronephrosis visible via ultrasound. In addition, a gravid uterus may displace the bowel allowing improved visibility of the appendix with an ultrasound. Otherwise, may order an MRI, if needed.
  4. Preferences for diverticulitis is dependent upon where a provider received his or her medical training. In Europe, ultrasound is the firstling imaging tool to rule out diverticulitis.

Views on plain film

Positioning the patient for x-ray is an important consideration in patients with abdominal complaints, whether it is supine, upright PA, or posterior-to-anterior and lateral chest radiographs. Upright abdominal imagining does not permit visualization of the ureter; however, would be needed to rule out lower lobe pneumonia, which can mimic abdominal pain. With a kidney, ureter and bladder (KUB), the patient is lying down to permit visualization of the kidneys, ureter and bladder by spreading out the mesentery. Furthermore, supine abdominal images can show dilated loops and calcifications.

Barium enema rarely done for diverticulitis. Barium contrast enema has been used for diverticulosis, but patient comfort and time to complete imaging exam usually precludes the study from being performed.

  1. What should provider look for? Abnormal findings include an ileus or obstructive gas pattern, a soft tissue mass, or pneumoperitoneum. Free air may be present in up to 12% of cases.5
  1. If an x-ray has been performed an x-ray and let’s say the plain films suggest a diagnosis of diverticulitis but is not definitive, CT should be ordered as the next step.

Prior to the advent of CT, contrast enema evaluation of the colon was the examination of choice for the diagnosis of diverticulitis. Occasionally ordered, but sensitivity is less than CT. Enema is contraindicated during the active phase of inflammation especially, the first 2 weeks of the acute episode.

Contraindication for the CT exam

  1.  Avoid scanning pregnant patients. Radiation exposure to a fetus can cause developmental problems. Thus, CT should only be performed for pregnant patients in critical situations and only after discussion of the potential risks. CT should be performed it it is necessary and in a life threatening situation for the mother. For instance, flank pain, fever, and history of kidney stones or suspected ruptured appendicitis.
  2. Avoid scanning patients with an allergy to the IV contrast media (IVCM), unless the benefit outweighs the risk.

Shellfish allergy does not exclude CT with IV contrast. It is not a true statement that shellfish allergy indicate an allergy to iodine contrast media. However, if a CT with contrast in absolutely necessary, such as to locate a tumor, precautionary measures can be implemented. This would include benadryl and corticosteroid therapy administered over a 13 hour timeframe prior to a contrast study.

Renal impairment may also prohibit patients from having contrast medium. An eGFR 60 and above is considered normal. If a patient’s eGFR is above 30, usually the patient may receive some dose of contrast safely. Previously, the school of thought was pre-treating the patient with N-Acetyl cysteine and hydration was renal protective. Although hydration is important, it is not renal protective. Any patient greater than 55 yo with a history of diabetes would be sent to get there GFR measured prior to the exam. Each institution determines what the contrast load will be or what is an acceptable GFR prior to administering contrast medium.

It be prudent for the nurse practitioner to check with the radiology department to determine if your patient will require IV contrast medium and what the policies are regarding its use for the above conditions, before referral.

Second Clinical Scenario

72 yo male patient with generalized abdominal pain and fever. Patient’s lab results are non-specific or normal. Why does he not have WBC elevation with a fever? Can he not make an immune response or is he not sick enough? Is it a neoplasm and not able to make an immune response? The range of pathology that can produce abdominal pain and fever is pretty broad. If we rule out neoplasm and the patient has a low grade fever and is not toxic, and we are thinking of gastroenteritits, then we can do a watchful waiting. If the patient is looking toxic the next day then imaging would be prudent.

Consider the following differentials:

  1. Pneumonia
  2. Hepatobiliary disease
  3. Gastroenteritis
  4. GI perforation
  5. Complicated pancreatic process
  6. Bowel obstruction or infarction
  7. Abcesses in the abdomen or tumor

Fever may dictate need to act quickly. If hepatobiliary disease can be excluded, then CT would be the imaging technique of choice, especially with a fever.

Third Clinical Scenario

A 21 year old male with right lower abdominal pain, low grade fever and with a WBC count greater than 11.5….as the provider, we are now beginning to suspect appendicitis

The test of choice would be CT with contrast of the abdomen/pelvis. In patients with smaller, thinner body habitus, may consider an ultrasound to spare a young person radiation exposure. However, a CT scan would be necessary to rule out perforation or access.

The Alvarado Score is a checklist that can give a strong reassurance of appendicitis:

  • right lower quadrant tenderness
  • fever
  • rebound tenderness
  • anorexia
  • nausea
  • vomiting
  • leukocytes greater than 10,000

However, due liability many surgeons prefer a CT scan rather than relying on The Alvarado Score.

Keep in mind that unnnecessary surgery for suspected appendicitis exposes patients to increased risks, morbidity, and expense, as well. In 1997, 261,134 patients underwent non-incidental appendectomies in the United States. However, 39,901 (15.3 percent) of the appendectomies showed no pathologic features of appendicitis.

Fourth Clinical Scenario

First time presentation of a 62 yo male patient with epigastric abdominal pain, mild tenderness radiating to the back and rapidly increasing in severity without pain relief. Patient with past medical history of hypertriglyceridemia, bowel sounds normal without splenomegaly nor hepatomegaly.

Consider the following differential diagnoses:

  1. Younger patient: alcoholic pancreatitis
  2. Older patient: pancreatic carcinoma, perforated ulcer or heart attack

What is my best diagnostic test?

In a young patient with medium to low suspicion order labs and instruct patient to return to the office the next day to review lab results evaluate pain if the patient does not seem that toxic. Lipase and amylase should be assessed, as lipase may rise within 4 – 8 hours of pancreatic symptom onset and peat after 24 hours of symptoms. With pancreatitis, lipase values will be 3x normal value, and is very useful as it will remain elevated for about 15 days of symptom onset. Consider ordering right upper quadrant ultrasound to assess for stone obstruction causing the pain. Lipase elevation is a good positive predictor of acute pancreatitis compared to amylase results. Many providers have stopped relying on serum amylase in favor of the serum lipase. However, although lipase has a high specificity for pancreatitis, it has a low sensitivity for pancreatitis. Another words, lipase may be normal in some circumstances.

Elevated liver enzymes with abdominal pain would indicate need for consideration of cholelithiasis, chronic alcoholism, as elevated liver enzymes are not always reliable indicators of pancreatic injury, but can help with understanding the extent of the injury. With elevated liver enzymes, perform an ultrasound. If the patient had presented after 72 hours of upper abdominal pain and concerned for necrosis, CT scan would be the imaging choice.

The opinions expressed in this podcast are solely that of Dr. Vachon and not of the US Navy, DOD, ABR, ACR or any other entity.

_______________________________________________________________________________

Contact Information For Dr. Ty Vachon MD:
Website: ORA Informatics
LinkedIn: Ty Vachon, MD
Twitter: @helpfulrads
Google+: Ty Vachon

Contact Information For Dr. Cynthia Jaffe DC, MSN, FNP-C, FIAMA:
Twitter: @drcjaffe
Website Blog: Health Scope News

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