USMLE® Step 2 CK Question of the Day: Ventral hernia repair

Learn the cause of post-operative symptoms in a 62-year-old woman following a ventral hernia repair with mesh. Explore her medical history, vital signs, and pulmonary examination findings. Learn more now and understand the potential factors affecting her condition. Enhance your medical knowledge with this USMLE® Step 2-style practice question.

A 62-year-old woman is admitted to the hospital after undergoing an uncomplicated ventral hernia repair with mesh. On post-op day 2 the patient feels short of breath and is having incisional site pain. She has had a bowel movement and is passing gas. She does not have chest pain, nausea, vomiting, urinary urgency or dysuria. Her medical history is significant for a 30 pack-year smoking history, hypertension, and diabetes. Temperature is 100.6°F (38.1°C), blood pressure is 140/82 mmHg, pulse is 98/minute, respiratory rate is 22/minute, and oxygen saturation is 92% on room air. On pulmonary examination, the patient has increased work of breathing, crackles in the lung bases bilaterally and dullness to percussion. There is no significant abdominal tenderness, erythema, edema or purulent drainage around the incision site. Which of the following is the most likely cause of this patient’s current condition? 

A.  Atelectasis

B. Acute transfusion reaction

C. Urinary tract infection

D.  Surgical site infection

E. Clostridium difficile infection

The correct answer to today's USMLE® Step 2 CK Question is...

A. Atelectasis

Before we get to the Main Explanation, let's see why the answer wasn't B, C, D, or E. Skip to the bottom if you want to see the correct answer right away!

Incorrect answer explanations

B. Acute transfusion reaction

Incorrect: Acute transfusion reactions present within the first 24 hours after surgery with the transfusion of blood products. This patient does not have a history of receiving a blood transfusion and is two days post-op.

C. Urinary tract infection

Incorrect: Urinary tract infections usually present between postoperative days 3 to 5, with urinary frequency, urgency, and lower abdominal pain or pressure. This patient has none of these symptoms. Patients with indwelling foley catheters are at increased risk for UTIs.

D. Surgical site infection

Incorrect: Surgical site infections usually present between postoperative days 5 to 7 with incisional pain. Physical exam often demonstrates erythema, edema, purulent drainage, a fluctuant mass, and tenderness to palpation at the incision site.

E. Clostridium difficile infection

Incorrect: Clostridium difficile infections typically present between weeks 1 to 4 post-op. Patients present with abdominal pain, watery diarrhea, nausea, and a history of antibiotic use.

Main Explanation

This patient is 2 days out from ventral hernia repair with mesh and presents with difficulty breathing, fever, and crackles in bilateral lung bases, suggestive of atelectasis–a common cause of postoperative fever within the first 2 days following surgery. Risk factors for atelectasis include incisional pain, shallow breathing with poor alveolar recruitment, depressed cough from narcotics, prolonged bed rest, and smoking history.

Postoperative fever is defined as a systemic body temperature that is at or above 38°C or 100.4°F within the postoperative period which gets divided into 4 phases based on the timing of the fever: immediate, acute, subacute, and delayed. 

An immediate postoperative fever occurs within 24 hours of the procedure. The most common cause is physiologic, but life-threatening complications such as acute transfusion reactions or adverse drug reactions can also occur. Physiologic fevers are transient, self-limited, and tend to occur following surgeries involving high levels of tissue trauma. Acute transfusion reactions should be suspected in patients who received blood products or have a personal or family history of transfusion reactions. Physical exam findings include flushing, skin rash, angioedema, respiratory distress, or hypotension. An adverse drug reaction can occur if the patient receives anesthetics, antibiotics, or other medications. 

The acute phase of postoperative fever occurs between postoperative days 1 to 7. The causes of fever during this time are recalled using the 5 Ws:

• Wind - Atelectasis or Pneumonia

• Water - Urinary Tract Infection

• Wound - Surgical Site Infection - superficial and deep

• Walking - Vascular causes - DVT, phlebitis, central line infection

• Wonder Drugs - Drug Fever

Subacute postoperative fever occurs between weeks 1-4 post-procedure. There are 2 important diagnoses that should not be missed during this time: anastomotic leaks and clostridium difficile infection. In an anastomotic leak, patients will present with abdominal pain, fever, nausea, vomiting, constipation, or obstipation after abdominal surgery. Physical exam will reveal abdominal tenderness, distension, and signs of peritonitis (such as rebound, guarding, and decreased bowel sounds). The use of antibiotics increases the risk of Clostridium Difficile infection. Patients will complain of colicky abdominal pain, watery diarrhea, nausea, abdominal tenderness, and distension.

Lastly, the delayed phase of postoperative fever occurs more than 30 days after the procedure. Most fevers that occur at this stage are unrelated to the surgery and caused by community infections such as upper respiratory infections. However, device or prosthesis infections and fistula formation are two complications that should not be missed. A device or prosthesis infection should be considered when there is intraoperative device implantation (such as mesh during hernia repair, ICD) or prosthesis implantation during joint replacement surgery. Patients will present with erythema, edema, and tenderness around the implantation site. Fistulas may occur in patients that have undergone resections requiring anastomosis or postoperative chemoradiation. They often present with erythema, tenderness, foul discharge, or bleeding from a visible fistula site. 

Major Takeaway

The timing of a fever that develops postoperatively is important for identifying the most likely underlying cause. The timing after the surgery can be divided into 4 phases: immediate (within 24 hours), acute (POD 1-7), subacute (between 1-4 weeks), and delayed (more than 30 days). 

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