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Diagnosis Deconstructed

Diagnosis Deconstructed: The Specificity Doctor

Morchi, Ravi MD

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doi: 10.1097/01.EEM.0000428930.96029.9b

    This man's arm has been through a lot: a local community hospital two weeks ago and our ED three days ago. Today, it came back. Something is surely wrong. But why has the problem not been solved?

    Upper extremity ultrasound. An ultrasound was negative for axillary and brachial vein DVT on initial presentation to an outside ED 14 days ago.

    Radiographs. No carpal, metacarpal, or long bone fracture.

    Labs and vitals. A normal white blood cell count. Multiple afebrile oral temperature readings. No tachycardia and no tachypnea.

    Aspiration. Aspiration of the wrist showed 11,000 white blood cells but no organisms or crystals at a visit to our institution three days ago.

    Hand consultant. Evaluations by two emergency physicians during the prior visit yielded no satisfying diagnosis so they asked for help. Despite a negative aspirate, the hand consultant falls back on the diagnosis of gout. It was arranged for the patient to return to our ED for a recheck. They knew something was wrong.

    CT angiogram of the left upper extremity. Today the patient was seen by a third EP and noted to have an abnormal radial-to-radial BP index suggesting limb ischemia. A CT angiogram was ordered and read as suboptimal contrast bolus, but otherwise intact brachial, radial, ulnar, and interosseous vessels.

    Now, during sign-out rounds, I am told the patient has been given a diagnosis of cellulitis. I am suspicious. It does not take this many dollars to diagnose cellulitis. The sensitivity doctor in all of us has said something is wrong. The temptation after all this time and money is to make it fit, whether the arm agrees or not. But I say the specificity doctor in us has to speak up. Just what is that something?

    Entering the room, I become his sixth physician in two visits to this hospital. Our resident accompanies me. She has seen him before on the prior evaluation when he was discharged with treatment for gout. He is understandably frustrated, and wants nothing to do with us.

    From the doorway, I see his hand and forearm are tense and swollen. Every few minutes he will shake it vigorously. It hurts. He feels it falling asleep, and has to stir up normal sensation with motion. Raising the limb or letting it hang dependent do not seem to alter the discomfort.

    He certainly has had an expensive and thorough evaluation already. But was it thorough in the right way? Having had his share of pixels, ultrasound waves, and needles, he agrees to just one more thing, and then wants to be discharged because he feels we are doing nothing for him. That sounds reasonable. Better make this last test cheap and worth his time.

    Shoulder. Palpating the AC joint, distal clavicle, and coracoid are painless. Just lateral to the coracoid and medial to the humeral head, you can jab three straightened fingers into the joint and he does not flinch. Glenohumeral rotation, flexion, and extension are unimpeded.

    Axilla. Mobile nodes. No tenderness on deeper palpation into the area of the axillary artery and vein.

    Upper arm. Superiorly his tissue is soft, and inferiorly it becomes edematous. With two-handed AP compression proximally and distally, he has no pain in the humerus. Running up and down pinching his biceps and triceps muscles between my thumb and fingers does not bother him. He can actively flex and extend at the elbow. The problem is not in muscle of the upper arm.

    Elbow. His soft tissue is edematous, but I cannot feel any bulge particular to the joint space in the center of the triangle delineated by his olecranon, lateral epicondyle, and radial head. He can passively flex and extend at the elbow as well as supinate and pronate. The problem is not ligament, bone, cartilaginous plate, or synovial lining at this joint.

    Forearm. Soft tissue is tense, more so as I move distally toward the wrist. AP compression between the radius and ulna is uneventful. Bones and interosseous membrane preserved. Active flexion of the wrist is strong. FCR, PL, FCU muscle bellies, and tendons are intact. Extension at the wrist is limited, but no pain with the pinching technique. ECRB, ECRL, and ECU muscles are not the answer. Next.

    Wrist. Edema is most tense over his volar wrist. He has a longitudinal scar here from a prior open carpal tunnel release years ago. There is no pain tapping over the wrist joint or volar carpal area. Passive flexion of the wrist is fine, but he has pain at the extreme of extension. I know what this is. Just a few more maneuvers to close out.

    “Point to where that hurts.” He makes a swirling motion with his asymptomatic hand encompassing the entire distal, swollen left limb.

    Hand. The most prominent finding is a firm hump of dorsal edema. It is a typical finding: lymphatics drain from the palm to the back of the hand where skin is loose and edema can build up. It is impressive on inspection, but the problem is rarely on the dorsum. It is a false localizer. But it does tell us we are close.

    Thenar muscles are soft. Thumb abduction, adduction, and flexion are intact. APB, ADP, and FPB are normal. He has some limitation to opposition of his thumb and small finger. I sense it is because of the obstructing effects of interposed edema, not to a problem with the muscles themselves. Hypothenar muscles and fifth digit function are similarly benign.

    Fingers. His pads are thick and creases filled with dark grime from years of manual work. They are swollen and in a slightly flexed position, but there is no volar tenderness over any of their tendon sheaths. He cannot make a fist. Flexion limited by edema in the palmar area. And then the telltale sign: passive extension of his fourth and fifth digits, and he jumps in pain. Is this a Kanavel's sign?

    Not exactly. He has inflammation in an area where tendons run. Impairing their passive extension and their active use, but that area is not the digital tendon sheath.

    “Where does it hurt when I do that?” Another swirling motion.

    “No. Exactly where? Show me.” His right index finger points to the problem.

    I press there, and he jumps. Tenderness proximally in his palm just between his thenar and hypothenar muscles. An infection here irritates flexor tendons destined for his third and fourth fingers, limiting passive extension. This is a midpalmar space infection.

    Over time, vascular and lymphatic recruitment engulfed his entire hand, forearm, and radiohumeral periarticular area in subcutaneous edema. Lymphatics working hard still could not clear the dorsal hump. The midpalmar process decompressed through the space of Parona into his forearm, producing volar carpal edema so tense that the radial artery was encircled by it. The result? A falsely low BP index simulating upstream arterial occlusion.

    Was he ischemic? Yes, but not from a luminal arterial obstruction. Rather from increased midpalmar space pressure that had risen above capillary pressure. Perfusion in the vasa nervorum is then compromised, and he feels the numb and prickly pain of his hand falling asleep. He shakes it vigorously to improve flow. His midpalmar space infection had produced a “compartment” syndrome to the hand although it did not occur in a formal muscular compartment.

    We started IV antibiotics and directed the hand surgery resident to the diagnosis. He was admitted, and had drainage of the midpalmar space via extension of the old longitudinal carpal release scar. The exudate retrieved grew out coagulase-negative Staphylococcus, for which infectious disease consultants would recommend continuing inpatient Vancomycin.

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