Hummingbird sign and penguin sign are radiographic signs seen on imaging studies that can indicate certain medical conditions. The terms refer to the appearance of the intestines in the image, which look similar to a hummingbird or penguin.
What causes hummingbird sign?
Hummingbird sign is seen when a part of the small intestine is fixed in position, often by scarring from surgery or inflammation. This fixed area of small bowel loops around the point of fixation, while the nearby small bowel remains mobile. On imaging studies, the resulting appearance looks similar to a hummingbird with its wings outstretched.
Some key causes of hummingbird sign include:
- Adhesions – Scar tissue binding the intestine can occur following abdominal surgery or episodes of infection and inflammation.
- Crohn’s disease – This inflammatory bowel disease can cause fibrosis and scarring that may fix sections of small bowel in place.
- Abdominal tuberculosis – Inflammation from abdominal TB can also create adhesive bands attaching the intestines.
- Radiation enteritis – Radiation therapy for cancers in the abdomen can damage the intestines and cause strictures.
- Small bowel obstruction – Any obstruction may result in a section of fixed small intestine with more mobile loops proximal to the obstruction.
What does penguin sign mean?
Penguin sign refers to the characteristic appearance of the distal esophagus on an upper GI series in patients with esophageal achalasia. In this disorder, the lower esophageal sphincter fails to relax normally and has a very high resting pressure. As a result, the esophagus becomes dilated and fluid-filled, with a tapered “beak-like” narrowing at the lower end.
On imaging, this creates a silhouette like a standing penguin, with a large round body (the dilated esophagus) and a tapering lower portion (the unopened sphincter). Penguin sign is considered diagnostic for achalasia.
How are hummingbird and penguin sign seen?
Hummingbird and penguin signs are most commonly seen on the following imaging studies:
- Barium swallow study – This type of X-ray study using oral barium contrast is optimal for seeing penguin sign in cases of achalasia. It may also detect instances of hummingbird sign.
- Barium enema – A barium enema X-ray study can highlight fixed loops of small bowel in hummingbird sign.
- CT abdomen – CT scans with oral and/or IV contrast may demonstrate penguin or hummingbird signs.
- MRI abdomen – MRI enterography images can also reveal these signs.
What is the significance of these signs?
Identifying hummingbird or penguin sign on abdominal imaging is important because these signs indicate:
- Bowel obstruction – Hummingbird sign often represents a partial small bowel obstruction, which may be chronic or recurring if caused by adhesions.
- Achalasia – Penguin sign is diagnostic of esophageal achalasia, a motility disorder.
- Underlying pathology – Both signs suggest prior surgery, inflammation, infection, radiation injury, or other conditions as the cause.
- Need for treatment – Detecting these signs helps guide appropriate treatment, which may range from anti-inflammatory medications to antibiotics to surgery.
How are these conditions treated?
Treatment depends on the underlying cause of hummingbird or penguin sign, but may involve:
- Achalasia:
- Medications to relax the lower esophageal sphincter
- Endoscopic procedures such as pneumatic dilation or botox injections
- Surgery (Heller myotomy)
- Small bowel obstruction:
- Conservative treatment with IV fluids and bowel rest
- Medications to reduce inflammation
- Surgical lysis of adhesions
- Crohn’s disease:
- Medications to reduce inflammation (aminosalicylates, steroids, immunosuppressants)
- Biologics targeting TNF-alpha or other inflammatory mediators
- Surgery for refractory disease (resection, strictureplasty)
- Infection:
- Antibiotics specific to the organism
- Draining collections or resecting involved bowel segments
In many cases, a combination approach is used. Treating the underlying condition can allow the intestine to return to normal mobility and function.
What is the prognosis with these signs?
The prognosis depends greatly on the underlying cause:
- Achalasia:
- Generally good prognosis, with normal life expectancy if treated
- Symptoms and imaging improve after therapy
- Possible recurrence over time requiring repeat treatments
- Adhesions:
- Variable prognosis depending on severity of obstruction
- Low-grade obstruction can be managed conservatively
- High-grade or complete obstruction requires urgent surgery
- Obstruction may recur after surgery due to adhesions reforming
- Crohn’s disease:
- Waxing and waning disease course
- Medications can induce long remissions but relapses may occur
- Stricturing complications worsen prognosis
- Nutritional support and surgery are sometimes needed long-term
- Infection:
- Prognosis good if infection treated appropriately
- Delays in diagnosing abdominal TB worsen outcomes
- Surgical resection may be needed for necrosis or perforation
Close follow-up is recommended in all cases to monitor for recurrence of obstruction or progression of the underlying condition.
Conclusion
In summary, hummingbird and penguin signs are characteristic radiographic findings that can diagnose important gastrointestinal conditions:
- Hummingbird sign indicates a portion of fixed small bowel, often due to adhesions or stricturing Crohn’s disease.
- Penguin sign is pathognomonic for esophageal achalasia, showing a dilated, fluid-filled esophagus with tapered narrowing at the lower esophageal sphincter.
- Identifying these signs guides appropriate treatment of the underlying pathology, which may include medications, endoscopic procedures, or surgeries.
- The prognosis depends on the severity of obstruction or motility disorder as well as response to therapy.
- With proper treatment, many patients achieve good outcomes and relief of their symptoms.