CASE REPORT 
Annals of Nuclear Medicine Vol. 4, No. 3, 111-113, 1990 
Technetium-99m MDP scintigraphy of rhabdomyolysis induced by exertional heat stroke : A case report . 
Teruhito MOCHIZUKI,* W. Newlon TAUXE,* and Joshua A PERPER** , ***
University of Pittsburgh School of Medicine, *Department of Radiology, Division of Nuclear Medicine, **Department of Epidemiology, and ***Allegheny Country Coroner's Office, Pittsburgh, PA, USA 
A case of rhabdomyolysis induced by exertional heat stroke in a police officer recruit is reported. Technetium-99m methylene diphosphonate scintigraphy demonstrated marked uptake of the injured skeletal muscle. This bone-scanning agent provided an excellent means of localizing and evaluating the muscle injury of rhabdomyolysis. Nuclear medicine physicians should be aware of the special conditions and causes in which bone scan may demonstrate striking findings. 
Key words : rhabdomyolysis, 99mTc-methylene-diphosphonate(99mTc-MDP), heat stroke, exercise 
INTRODUCTION 
RHABDOMYOLYSIS, a clinical and laboratory syndrome, can be caused by many conditions (Table 1) and is the result of lysis of skeletal muscle with release of cell contents, such as myoglobin and muscle enzymes.1,2 Although technetium-99m methylene diphosphonate (99mTc-MDP) is a widely used bone-scanning radiopharmaceutical, such phosphonate bone-scanning agents are also very useful for the evaluation of the myocardial3 and skeletal muscle4-13 injury. We report a case of rhabdomyolysis induced by heat stroke whereby skeletal muscle injury was strikingly demonstrated by 99mTc-MDP scintigraphy. Nuclear medicine physicians should be aware of the conditions which may cause rhabdomyolysis and of its remarkable 99mTc-MDP findings. 
Received June 26, 1990, revision accepted August 29, 1990. For reprints contact : W. Newlon Tauxe, M.D., Division of Nuclear Medicine, Department of Radiology, Presbyterian University Hospital of pittsburgh, DeSoto at O'Hara Streets, Pittsburgh, PA 15213 
CASE REPORT 
A 25-year-old male police officer recruit performed intense physical exercise on the first day of training. The outdoor temperature was 27deg.C, and he was severely dehydrated. After several hours of hard training, and while running, he collapsed into convulsions and was pale and unresponsive. On arrival at a nearby hospital, he was unconscious, and his body temperature was 40.5deg.C. Physical and laboratory examination revealed muscle swelling, myoglobinuria and increased creatinine phosphokinase (CPK). A diagnosis of exertional heat stroke with rhabdornyolysis was made at that time. On the fifth day after collapse, the patient was comatose, anuric, and his general condition was poor. Laboratory findings were as follows : urine myoglobin (+), RBC 320x104/mm, CPK>32,000 IU/l, T. Bilirubin 11.O mg/dl, sGOT 5,191 IU/ml, sGPT 7,276 IU/ml. He developed acute renal failure, fulminant liver failure and encephalopathy. On the seventh day after collapse, he was sent to our hospital, for evaluation of the liver, and if indicated, liver transplantation. Since the liver insufficiency was severe, a liver transplantation was performed on the 8th day. Over the next two weeks, he became responsive and his overall conditions improved to some extent.On the 23rd day, the patient underwent 99mTc-MDP scintigraphy for the evaluation of muscle injury. The scan demonstrated marked uptake of the injured skeletal muscles (Fig.1). Two days later (25th day), a biopsy from left deltoid muscle was obtained. Electron microgram revealed numerous myofibers under going distruption of sarcomeres and fragmentation of Z-bands. Intrasarcoplasmic vacuoles were noted in some myofibers. The CPK levels were plotted as a reference of muscle unjury in Figure 2. On the 45th day, the patient died from other ccunplications, namely cerebellar hemorrhage from mycotic aneurysm, sepsis, renal failure, pancreatitis and pneumonia. 
DISCUSSION 
Many conditions may cause rhabdomyolysis (Table 1). Excessive physical exercise is one of the common cause,5,6 and may be more common in military recruits14 or in persons who are required to perform excessive physical exercise. Matin6 reported that 10 out of 11 runners who participated in a 50- to 100-mile "ultramarathon" showed 99mTc-pyrophosphate uptake as a result of muscle injury during the 24-to 48-hour period after the race. After such extreme exercise, the incidence of exertional rhabodomyolysis might not be so rare. In addition to the primary symptoms of muscle swelling or edema, myalgia and pigmenturia, multiorgan complications may develop related with rhabdomyolysis. As shown in our case, severe exertional heat stroke accompanied by dehydration is more likely to cause renal failure, liver dysfunction, and central nervous system (cerebellar) damage, since these organs are particularly sensitive to heat exposure. Acute renal failure due to myoglobin plugs15 requires immediate therapy (diuretics or dialysis, both of which were required for our patient) ; however, renal failure is usually reversible if the patient survives the acute phase. Hypokalemia is another condition that may develop, especially during the first three days, and it may cause lethal dysrhythmia. In most cases, liver damage is not severe; however, our patient developed fulminant liver failure. The central nervous system, especially the cerebellum, is well known to be very sensitive to heat.16 To avoid these complications, early diagnosis is required. 99mTc-phosphate scintigraphy is very sensitive to muscle injury. Since the incidence of positive findings decreased gradually after a week, the nuclear medicine physicians should be aware of the duration of these findings so that proper interpretation may be made. The degree to which the scan is positive also depends on the severity of the injury. Moreover, the muscle injury may continue and/or recur. In such cases, prolonged visualization of the injured muscle can be observed. These findings are similar to those of acute myocardial infarction which shows positive during the first to sixth day.3 Some of these scans show prolonged uptake. Our patient underwent 99mTc-MDP scintigraphy on the 23th day after the principal muscle injury occurred. Although the serum myoglobin was negative and aldolase was at the upper limit of the normal range at this time, CPK was still high (6,000-9.000 IU/l) (Fig. 2). Therefore, some degree of muscle damage seemed to be continuing. If the patient had received the scan earlier, uptake in the lesions may have been even more striking. We demonstrated a severe case of rhabdomyolysis caused by exertional heat stroke with multi-organ complications. Muscle injury was strikingly visualized with 99mTc-MDP scintigraphy. 
ACKNOWLEDGMENT 
The authors thank Ms. Meg Sachse and Ms.Judith K Holden for their kind and fine reviewing and preparing the manuscript. 
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