Okay, let's tackle this question. The patient is a 61-year-old woman with nausea, vomiting, left-sided abdominal pain, low-grade fever, and increased neutrophils. The key here is to figure out the most likely diagnosis from the given options. Since the options aren't listed, I need to consider common causes of acute left-sided abdominal pain in older adults.

First, left-sided abdominal pain could be due to several conditions. Let's think about the possible differentials. Diverticulitis comes to mind, especially in the elderly. It's an inflammation or infection of a diverticulum in the colon, usually the sigmoid colon, which is on the left side. Symptoms include lower left abdominal pain, fever, nausea, and leukocytosis with increased neutrophils. That fits the presentation here.

Another possibility is diverticulitis versus other conditions like diverticular bleeding, but bleeding is usually painless. Then there's the possibility of other GI issues like peptic ulcer disease, but that's more upper abdominal. Ovarian issues in women could present with lower abdominal pain, but the fever and neutrophils point more towards an infectious/inflammatory process.

Let's consider other options. Pancreatitis typically presents with upper abdominal pain, often radiating to the back, and is associated with elevated amylase/lipase. Cholecystitis is right upper quadrant pain. Constipation can cause colonic distension, but the presence of fever and neutrophils suggests infection.

So, diverticulitis is the most likely. The increased neutrophils indicate an acute infection. Diverticulitis is common in the elderly, which aligns with the patient's age. The clinical features match: sudden onset, left-sided pain, fever, and leukocytosis. Other options don't fit as well. For example, if it were diverticulosis without inflammation, there might not be fever or neutrophilia.

I need to make sure I'm not missing other possibilities. Left-sided appendicitis is rare, but possible. However, the classic presentation of diverticulitis is more consistent here. Also, the presence of neutrophils points to infection rather than just inflammation.

So, the correct answer should be diverticulitis. The other options like ovarian torsion, ectopic pregnancy, or other GI issues don't fit the fever and neutrophil increase. The key here is the combination of symptoms and lab findings pointing to an infectious/inflammatory process in the left colon.

**Core Concept**
This question assesses the differential diagnosis of acute left-sided abdominal pain in an elderly patient, focusing on **diverticulitis** as a classic cause. Key features include **lower left quadrant pain**, **fever**, and **leukocytosis with neutrophilia**, indicating acute inflammation or infection.

**Why the Correct Answer is Right**
Diverticulitis occurs due to inflammation or infection of diverticula (outpouchings) in the colon, most commonly the **sigmoid colon**. The patient’s symptoms—nausea, vomiting, sudden left-sided pain, fever, and neutrophilia—align with acute diverticulitis. Neutrophil increase reflects localized bacterial infection, often from **Gram-negative bacteria** (e.g., *E. coli*) or **anaerobes**. Imaging (

✓ Correct Answer: C. Diveiculitis