Establishing a Diagnosis

A 52-year-old woman is evaluated in the emergency department for left lower quadrant abdominal pain and fever that began 24 hours ago. The pain is constant and severe. Her past medical history is significant for obesity and chronic constipation. Her temperature is 38.3°C (100.9°F), blood pressure is 128/82 mm Hg, pulse is 98/min, and respirations are 16/min. Physical examination reveals focal tenderness to palpation in the left lower quadrant with voluntary guarding, but no rebound tenderness or rigidity. Laboratory studies show a leukocyte count of 16,500/mm³. A computed tomography (CT) scan of the abdomen and pelvis with intravenous and oral contrast demonstrates focal wall thickening of the sigmoid colon, prominent pericolic fat stranding, and an adjacent 4.5-cm well-circumscribed, rim-enhancing fluid collection. No free intraperitoneal air is observed. Based on these imaging findings, which of the following is the most appropriate next step in management?

A 32-year-old woman, G2P1, at 18 weeks gestation is brought to the emergency department by emergency medical services. Her husband reports that she suddenly lost the ability to speak and developed severe weakness on her right side approximately 45 minutes ago. Upon arrival, her blood pressure is 145/88 mmHg, heart rate is 92/min, and respiratory rate is 16/min. Neurological examination reveals a dense right-sided hemiplegia, right lower facial droop, and global aphasia. Her National Institutes of Health Stroke Scale (NIHSS) score is 18. The patient is otherwise healthy, and her pregnancy has been uncomplicated. Suspecting an acute ischemic stroke with a possible large vessel occlusion (LVO), the clinical team prepares for immediate neuroimaging to determine her candidacy for reperfusion therapy.

Which of the following is the most appropriate initial sequence of imaging studies for this patient?

A 58-year-old woman is evaluated in the emergency department for sudden-onset severe dyspnea, lightheadedness, and right-sided pleuritic chest pain that began 2 hours ago. Two months ago, she underwent an uncomplicated total abdominal hysterectomy for uterine fibroids. On arrival, her temperature is 37.1°C (98.8°F), blood pressure is 108/68 mmHg, pulse is 112/min, and respirations are 24/min. Pulse oximetry shows 88% on room air. A computed tomography (CT) pulmonary angiogram reveals a large, occlusive filling defect in the main pulmonary artery extending into the right and left lobar branches. Additional review of the axial CT slices demonstrates a right ventricular to left ventricular (RV/LV) diameter ratio of 1.4, with leftward bowing of the interventricular septum, and reflux of contrast into the inferior vena cava. Immediately upon returning from the radiology suite, she becomes confused and diaphoretic; her blood pressure drops to 78/50 mmHg, and her pulse increases to 132/min. What is the most appropriate next step in patient management?

A 52-year-old man presents for evaluation of a new, irregularly pigmented 8-mm macule on his left shoulder. An excisional biopsy with 2-mm margins is performed. The synoptic pathology report reveals an asymmetric, poorly circumscribed proliferation of atypical melanocytes present as single cells and in variable-sized nests. These cells exhibit prominent upward pagetoid scatter throughout the full thickness of the epidermis. Atypical melanocytes are also noted invading the papillary and superficial reticular dermis to a measured depth of 1.1 mm from the epidermal granular layer. There is no evidence of surface ulceration, and the dermal mitotic rate is 2 mitoses per square millimeter. Deep and peripheral margins are free of tumor. Based on the interpretation of this pathology report, which of the following statements are correct? (Select all that apply)

An $8$-year-old boy is brought to the emergency department by his parents due to abdominal pain for the past $24$ hours. The pain initially began around his umbilicus but has now migrated to the right lower quadrant. He has had one episode of non-bilious vomiting and reports a complete loss of appetite. His temperature is $38.1^\circ\text{C}$ ($100.6^\circ\text{F}$), pulse is $105/\text{min}$, and blood pressure is $100/65\text{ mmHg}$. Physical examination reveals a patient who lies very still on the stretcher. Abdominal examination demonstrates significant tenderness to palpation in the right lower quadrant, particularly one-third of the distance from the anterior superior iliac spine to the umbilicus. Rebound tenderness is present. Laboratory studies show a leukocyte count of $14,500/\text{mm}^3$ with a neutrophilic predominance. Which of the following is the most appropriate initial step in diagnostic imaging?

Match the following classic gastrointestinal histopathologic biopsy descriptions with their corresponding definitive clinical diagnoses.

A physician is evaluating several patients presenting to the clinic with newly diagnosed or poorly controlled hypertension. Careful medical history evaluation is crucial for identifying secondary causes or exacerbating factors. Match each patient's presenting historical features with the most appropriate diagnostic consideration.

A physician is reviewing laboratory results for four different patients in the emergency department. Match each patient's combined arterial blood gas (ABG) and basic metabolic panel (BMP) profile with the most likely clinical diagnosis. Assume a normal reference range for serum anion gap is $8$-$12$ mEq/L.

For each patient scenario below, select the most appropriate next step in diagnostic imaging.

A 28-year-old woman presents to the ambulatory care clinic for evaluation of vague, intermittent right upper quadrant abdominal discomfort that has been present for the past three months. She has no significant past medical history other than a 10-year history of taking combined oral contraceptive pills. Vital signs are within normal limits, and physical examination reveals a soft, non-tender abdomen with no palpable hepatomegaly. Laboratory studies, including liver function tests, basic metabolic panel, alpha-fetoprotein, and CA 19-9, are all within normal limits. Given her persistent symptoms, a multiphasic contrast-enhanced magnetic resonance imaging (MRI) of the liver is performed. The MRI reveals a solitary, 6-cm, well-demarcated lesion in the right hepatic lobe. During the arterial phase, the lesion demonstrates robust, homogeneous hyperenhancement. On the portal venous and delayed phases, the lesion becomes isointense to the surrounding normal liver parenchyma. A central stellate structure is identified within the lesion; this structure is hyperintense on T2-weighted sequences and demonstrates progressive contrast enhancement on the delayed phase. Based on the precise interpretation of these imaging findings, which of the following is the most appropriate next step in management?

A 34-year-old man presents to the emergency department with a 2-day history of sharp, constant right lower quadrant abdominal pain. He reports no nausea, vomiting, or changes in bowel habits. His temperature is 37.2°C (99.0°F), blood pressure is 128/78 mmHg, and pulse is 82/min. Physical examination reveals localized tenderness to palpation in the right lower quadrant without rebound or guarding. Laboratory studies show a leukocyte count of 11,500/mm³. A contrast-enhanced computed tomography (CT) scan of the abdomen and pelvis is performed. The scan reveals a 2.5-cm, oval-shaped, fat-density lesion located anterior to the ascending colon, featuring a hyperdense rim and a central high-attenuation dot. There is mild surrounding inflammatory fat stranding. The colonic wall demonstrates normal thickness, and the appendix measures 5 mm in diameter with no surrounding fluid. Based on these imaging findings, which of the following is the most likely diagnosis?

An 76-year-old woman arrives at the emergency department accompanied by her daughter. The patient reports the abrupt onset of excruciating, generalized abdominal pain that started approximately $2$ hours ago. The pain is severe, constant, and associated with one episode of non-bilious emesis and an urgent need to defecate. Her medical history includes long-standing hypertension, type 2 diabetes mellitus, chronic kidney disease stage 4, and paroxysmal atrial fibrillation. She states she has not taken her prescribed apixaban for the past three weeks due to an insurance coverage issue.

Vital signs show a temperature of $37.1^\circ\text{C}$ ($98.8^\circ\text{F}$), blood pressure of $158/92 \text{ mmHg}$, a heart rate of $115/\text{min}$ with an irregularly irregular rhythm, and a respiratory rate of $22/\text{min}$. On physical examination, the patient appears in significant distress, writhing on the stretcher. Her abdomen is soft and non-distended. There is mild, diffuse tenderness to palpation, but no guarding, rigidity, or rebound tenderness is elicited. Bowel sounds are diminished.

Which of the following is the most appropriate next step in diagnostic imaging for this patient?

A 28-year-old woman, G1P0 at 16 weeks gestation, presents to the emergency department with a 12-hour history of progressively worsening right lower quadrant abdominal pain, nausea, and vomiting. Her temperature is 38.0°C (100.4°F), blood pressure is 112/72 mmHg, and heart rate is 105/min. Physical examination reveals focal tenderness in the right lower quadrant with guarding, but no rebound tenderness. Laboratory studies show a leukocyte count of 14,500/mm³. Which of the following is the most appropriate initial imaging study to establish the diagnosis?

A 55-year-old woman is evaluated in the breast clinic after a routine screening mammogram demonstrated a new cluster of fine, linear, and branching microcalcifications in the upper outer quadrant of her right breast. She has no palpable breast masses, skin dimpling, or nipple discharge. A stereotactic core needle biopsy of the calcifications is performed.

Histopathologic examination of the biopsy specimens reveals enlarged terminal duct lobular units completely expanded by a monomorphic population of atypical epithelial cells forming rigid, punched-out secondary lumens. The central portions of these involved spaces contain abundant eosinophilic amorphous debris with karyorrhectic nuclei. Associated microcalcifications are present within this central debris.

Immunohistochemical staining is performed and demonstrates a continuous, intact rim of p63 and smooth muscle myosin heavy chain (SMMHC) positive cells surrounding the involved spaces. The neoplastic cells exhibit strong, diffuse membranous staining for E-cadherin.

Based on the biopsy findings, which of the following is the most accurate diagnostic interpretation?

During a morning clinic session, a physician evaluates four different patients who are primarily complaining of involuntary shaking. Match each patient's specific physical examination finding and clinical history to the most accurate diagnostic etiology.

A 72-year-old man who is recovering from a right total hip arthroplasty performed 3 days ago develops progressive abdominal distension, mild diffuse abdominal pain, and nausea. He has not had a bowel movement since surgery, though he reports passing flatus. His medications include oxycodone, enoxaparin, and scheduled acetaminophen. Vital signs are temperature 37.1°C (98.8°F), blood pressure 130/80 mmHg, heart rate 88/min, and respiratory rate 16/min. Physical examination shows a massively distended, tympanic abdomen with hypoactive bowel sounds. There is no guarding, rigidity, or rebound tenderness. Laboratory results are unremarkable. A supine plain abdominal radiograph demonstrates diffuse dilation of the cecum, ascending colon, and transverse colon, with a maximum cecal diameter of 9 cm. There is a continuous column of gas extending down to the rectum with no discrete transition point. No free intraperitoneal air is visualized. Based on the interpretation of these imaging findings, which of the following is the most appropriate next step in management?

A $62$-year-old man with a $4$-year history of untreated, asymptomatic, low-grade follicular lymphoma presents with rapid enlargement of a right cervical lymph node, new-onset fevers, and a $10\%$ body weight loss over the past $6$ weeks. An excisional biopsy of the rapidly enlarging node is performed.

Histopathologic and molecular evaluation reveals the following:
- Complete architectural effacement by a diffuse infiltrate of large lymphoid cells.
- The atypical cells display vesicular chromatin, prominent nucleoli, and moderate basophilic cytoplasm.
- No residual nodular or follicular architecture is identified.
- Immunohistochemistry: The large cells are strongly positive for $CD20$, $CD10$, $BCL-2$, and $BCL-6$.
- The Ki-67 proliferation index is estimated at $85\%$.
- Fluorescence in situ hybridization (FISH) confirms the persistence of a $t(14;18)(q32;q21)$ translocation and identifies a newly acquired $MYC$ gene rearrangement at $8q24$.

Which of the following is the most accurate diagnostic interpretation of this lymph node biopsy?

Evaluate the following acute and subacute clinical presentations. For each patient scenario, select the single most appropriate next imaging modality based on diagnostic yield, clinical guidelines, and patient-specific contraindications.

A 58-year-old man with long-standing type 2 diabetes mellitus and peripheral neuropathy is evaluated in the clinic for a deep ulcer on the plantar aspect of his left foot. On examination, there is surrounding erythema and induration. A sterile metal probe reaches the deep fascia but does not definitively contact bone. Given the high clinical suspicion for underlying osteomyelitis, the physician decides to initiate a stepwise diagnostic imaging workup.

Arrange the following imaging modalities in the standard recommended sequence for evaluating suspected diabetic foot osteomyelitis, starting from the most appropriate initial test to the alternative advanced study reserved for patients with specific contraindications.

A 71-year-old man presents to the outpatient clinic with a 4-week history of progressively worsening yellowing of his skin and eyes, accompanied by generalized pruritus and a 6-kg (13-lb) unintentional weight loss. He reports that his urine has become dark like tea, and his stools are pale and clay-colored. He denies any abdominal pain, nausea, or vomiting. His medical history is significant for hypertension and type 2 diabetes mellitus. Physical examination reveals pronounced scleral icterus and a palpable, smooth, non-tender mass in the right upper quadrant of the abdomen. Laboratory studies show a total bilirubin of 14.2 mg/dL, direct bilirubin of 11.5 mg/dL, and an alkaline phosphatase of 780 U/L. The physician suspects a malignant biliary obstruction and initiates a diagnostic workup. Arrange the following imaging and image-guided modalities in the most appropriate chronological sequence for the evaluation of this patient's painless jaundice, proceeding from the initial diagnostic step to detailed staging and therapeutic intervention.