NAVLE Small Animal Diagnostic Imaging Questions and Answers — Questions and Answers
Question 1: A 5-year-old dog presents with acute vomiting and abdominal pain. Abdominal radiographs reveal a segment of small intestine that is severely dilated with gas, proximal to a segment of normal-caliber, empty-appearing small intestine. What is this radiographic finding, often referred to as 'two populations of bowel,' most indicative of?
- Functional ileus
- Mechanical obstruction (Correct answer)
- Gastroenteritis
- Pancreatitis
Correct answer: Mechanical obstruction
The presence of two distinct populations of bowel (one severely dilated and one normal or empty) is a classic radiographic sign of a complete or high-grade mechanical obstruction. The intestine proximal to the blockage becomes distended with gas and fluid, while the intestine distal to the obstruction remains empty. Functional ileus and gastroenteritis typically cause a more generalized, mild to moderate dilation of the intestines without a clear transition point.
Question 2: On abdominal ultrasound of a cat with stranguria, a hyperechoic structure is identified in the center of the urinary bladder. The structure produces a clean, dark vertical band beneath it that obscures deeper tissues. Which of the following best describes this artifact and the most likely identity of the structure?
- Reverberation artifact from a gas bubble
- Acoustic enhancement from a cyst
- Side lobe artifact from a polyp
- Acoustic shadowing from a urolith (Correct answer)
Correct answer: Acoustic shadowing from a urolith
A urolith (bladder stone) is a mineralized, dense structure that is hyperechoic (bright) on ultrasound. It strongly reflects or attenuates the ultrasound beam, preventing it from passing through to the tissues below. This creates a signal void, or 'acoustic shadow,' which appears as a dark band deep to the stone. A gas bubble would also shadow but typically creates a 'dirty' shadow with reverberation. A blood clot is typically hyperechoic but not dense enough to cause shadowing. A polyp is a soft tissue structure and would not cause shadowing.
Question 3: A 6-year-old Dachshund presents with acute onset of non-ambulatory paraparesis and spinal hyperesthesia localized to the T3-L3 region. Which imaging modality is considered the gold standard for definitively diagnosing intervertebral disc extrusion and assessing the degree of spinal cord compression?
- Magnetic Resonance Imaging (MRI) (Correct answer)
- Survey spinal radiography
- Computed Tomography (CT)
- Myelography
Correct answer: Magnetic Resonance Imaging (MRI)
Magnetic Resonance Imaging (MRI) is the gold standard for imaging the spinal cord and associated soft tissues. It provides excellent detail of the disc material, spinal cord parenchyma, and nerve roots, allowing for precise localization of the extruded disc and evaluation of secondary cord changes like edema or hemorrhage. While CT and myelography can identify cord compression, MRI offers superior soft tissue contrast without the need for intrathecal contrast injection.
Question 4: You are evaluating thoracic radiographs of an older cat with a history of a previously removed mammary carcinoma. The lung fields show multiple, well-defined, variably sized nodules of soft tissue opacity. Which of the following is the most likely interpretation of this pulmonary pattern?
- Fungal pneumonia
- Allergic bronchitis (asthma)
- Metastatic neoplasia (Correct answer)
- Cardiogenic pulmonary edema
Correct answer: Metastatic neoplasia
The presence of multiple, well-defined, soft tissue nodules (often called a 'cannonball' pattern, though they can be small) throughout the lung fields is the classic radiographic appearance of hematogenous metastatic neoplasia. Fungal pneumonia can also be nodular but is often less defined. Feline asthma typically presents with a bronchial pattern ('donuts' and 'tram lines'). Cardiogenic edema usually appears as an unstructured interstitial to alveolar pattern, often with a patchy distribution.
Question 5: A 4-year-old male Dalmatian has recurrent stranguria. Survey abdominal radiographs are unremarkable. Given this breed's predisposition to radiolucent uroliths, which contrast study is most appropriate to definitively identify their presence within the bladder?
- Excretory urogram
- Positive contrast cystogram
- Negative contrast cystogram
- Double contrast cystogram (Correct answer)
Correct answer: Double contrast cystogram
Dalmatians are prone to forming urate uroliths, which are often radiolucent and not visible on survey radiographs. A double contrast cystogram is the ideal study in this case. This technique uses a small amount of positive contrast medium to coat the bladder wall and any uroliths, followed by distention with negative contrast (gas). The radiolucent uroliths are then outlined by the positive contrast, making them visible against the dark, gas-filled lumen. A positive contrast study alone could obscure the stones.
Question 6: A 9-year-old dog is presented for chronic, unilateral nasal discharge. To evaluate the extent of disease, including potential bone destruction of the nasal turbinates and integrity of the cribriform plate, which advanced imaging modality is superior?
- Computed Tomography (CT) (Correct answer)
- Magnetic Resonance Imaging (MRI)
- Rhinoscopy with biopsy
- Dental radiography
Correct answer: Computed Tomography (CT)
Computed Tomography (CT) is the imaging modality of choice for evaluating the nasal passages because of its excellent spatial resolution and superior ability to detail bone. It eliminates the superimposition of structures seen on radiographs and is better than MRI for assessing fine bony changes like turbinate destruction or lysis of the cribriform plate, which is critical for staging nasal tumors or fungal disease. While rhinoscopy is needed for biopsy, CT provides the best anatomical map for surgical or radiation planning.
NAVLE Small Animal Diagnostic Imaging Questions and Answers
A 5-year-old dog presents with acute vomiting and abdominal pain.
Abdominal radiographs reveal a segment of small intestine that is severely dilated with gas, proximal to a segment of normal-caliber, empty-appearing small intestine.
What is this radiographic finding, often referred to as 'two populations of bowel,' most indicative of?