Serum Biochemical Abnormalities Research Articles

Part II: Liver function in oncology: towards safer chemotherapy use

The liver is fundamentally important in drug metabolism. In oncology, the astute clinician must not only understand the meaning and limitations of commonly ordered liver biochemical tests, but also be aware of which anticancer agents might induce liver dysfunction, and of the strategies for appropriate dosing of patients with pre-existing liver dysfunction. In part I of our Review, we highlighted both the importance and inadequacies of identifying serum biochemical liver abnormalities in oncology; we also discussed a lack of routine formal investigation of liver function. We summarised chemotherapy-related hepatotoxicity and other causes of liver toxic effects in patients with cancer. Here in part II, we discuss trials that have specifically assessed chemotherapy dosing strategies in the setting of overt biochemical liver dysfunction and we note their recommendations. Furthermore, we review other assessments of liver metabolic and excretory function, particularly in the setting of chemotherapy drug handling. We discuss the potential use of these metabolic probes in practice.

Assessment of acute injuries, exposure to environmental toxins, and five-year health surveillance of New York Police Department working dogs following the September 11, 2001, World Trade Center terrorist attack

To determine deployment logistics of New York Police Department (NYPD) working dogs that assisted in relief efforts at the World Trade Center (WTC) site following the September 11, 2001, terrorist attack; establish types and rates of related acute injuries and illnesses; identify environmental toxin exposures; and determine long-term (ie, 5-year) health effects of deployment. Prospective cohort study. 27 working dogs. Deployment logistics for the period from September 11, 2001, through May 30, 2002, were determined, and acute health disorders were identified by means of physical examination; a questionnaire; interviews with dog handlers; and toxicologic (blood and hair samples), clinicopathologic, microbiologic (nasal swab specimens submitted for Bacillus anthracis culture), and radiographic methods. Long-term health surveillance ended September 21, 2006. Dogs worked a total of 1,428 days (15,148 hours) at the site. Seventeen of the 27 (62.9%) dogs had health disorders during the first week. Specific conditions included fatigue (incidence rate [events/1,000 active deployment hours], 13.1), conjunctival irritation (13.1), respiratory tract problems (12.4), decreased appetite (10.8), dehydration (10), and cuts (9.3). Only minor hematologic and serum biochemical abnormalities were identified. Bacterial culture of nasal swab specimens did not yield B anthracis. Only mild and infrequent health conditions were identified during the 5-year follow-up period. None of the dogs were identified as having chronic respiratory tract disease. Six dogs died of various causes. Results suggested that acute injuries and illnesses were common among NYPD working dogs deployed to the WTC disaster site, but that longterm health complications were minimal.

Suspected albuterol toxicosis in a dog

A 6-year-old male castrated Shetland Sheepdog was evaluated because of severe hypokalemia and progressive paresis. Physical examination revealed fever, tachypnea, mydriasis, hyperemic mucous membranes, severe forelimb paresis, and hind limb paraplegia. The dog had superficial and deep pain sensation in all 4 limbs. Forelimb spinal reflexes were considered normal, but hind limb reflexes were normal to slightly hyperreflexive. The panniculus reflex was considered to be normal, and cranial nerve reflexes were intact. A CBC revealed mild leukocytosis and erythrocytosis, and serum biochemical analysis revealed severe hypokalemia. Thoracic and abdominal imaging did not reveal relevant findings. Blood pressure and ECG findings were within reference limits. Questioning of the owner revealed possible exposure to albuterol via ingestion of medication intended for the owner's horse. Results of serum testing via immunoassay were suggestive of albuterol toxicosis. Treatment included IV administration of an electrolyte solution and supplemental potassium chloride. The rate of potassium chloride supplementation was slowly decreased as serum potassium concentration increased. No other medical intervention was required, and the dog made a rapid and complete recovery. Ingestion of albuterol can lead to profound physical and serum biochemical abnormalities. Appropriate historical information should be obtained to identify possible sources and routes of exposure to intoxicants. Albuterol-induced hypokalemia can be successfully managed medically.

Oncogenic hypophosphataemic osteomalacia: biomarker roles of fibroblast growth factor 23, 1,25-dihydroxyvitamin D3 and lymphatic vessel endothelial hyaluronan receptor 1

Oncogenic osteomalacia (OOM) is characterised by tumour production of fibroblast growth factor 23 (FGF23) that results in hypophosphataemia and renal phosphate wasting, reduced 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) synthesis and osteomalacia. Here, we demonstrate the roles of serum FGF23 and 1,25(OH)2D3, together with the lymphatic vessel endothelial hyaluronan receptor 1 (LYVE-1), as biomarkers for OOM. A previously well 52-year-old man presented with a 2-year history of generalised musculoskeletal pain and proximal myopathy. He had hypophosphataemia, elevated serum alkaline phosphatase activity, low serum 1,25(OH)2D3 and a reduced tubular maximum of phosphate/glomerular filtration rate. These findings indicated a diagnosis of OOM, but magnetic resonance imaging (MRI) and octreotide scintigraphy did not identify any tumours. Treatment with oral phosphate and calcitriol resolved the symptoms and biochemical abnormalities within 6 months. Four years later, he relapsed whilst on treatment with oral phosphate and calcitriol. Serum FGF23 concentration was elevated and MRI identified a 2 cm tumour within Hoffa's fat pad of the left knee. Removal of the tumour resulted in a complete resolution of symptoms and normalisation of the serum biochemical abnormalities including serum FGF23. Histology demonstrated a phosphaturic mesenchymal tumour, mixed connective tissue variant (PMTMCT), which revealed immunostaining with anti-LYVE-1 antibody and hence the presence of lymphatic vessels. Serum FGF23 and 1,25(OH)2D3 were found to be reliable biomarkers for OOM. In addition, the demonstration of lymphatics in the PMTMCT helps to distinguish this tumour from most typical benign haemangiomas.

Exposure to Phenobarbital in a Foal after Nursing a Mare Treated with Phenobarbital

Exposure to Phenobarbital in a Foal after Nursing a Mare Treated with Phenobarbital

Effects of a single injection of methylprednisolone acetate on serum biochemical parameters in 11 cats

Therapeutic use of corticosteroids has been implicated in a variety of serum biochemical abnormalities in dogs; however, the effects in cats are less well characterized. The objective of this brief communication is to report serum biochemical changes in response to methylprednisolone acetate (MPA) in adult cats. Serum biochemical profiles were performed on 11 cats with dermatologic diseases at baseline, 3-6 days, and 16-24 days after a single intramuscular dose of 5 mg/kg MPA. Median serum albumin and bicarbonate concentrations and amylase activity were increased compared to baseline at both post-treatment time points; aspartate aminotransferase activity and magnesium concentration were increased at 3-6 days post-treatment only; and alkaline phosphatase activity and total calcium concentration were increased at 16-24 days post-treatment only. Median serum creatinine concentration was decreased compared to baseline at both post-treatment time points. Examination of data from individual cats revealed significant variability in serum biochemical changes in response to MPA. No adverse clinical reactions to the drug were reported. A single dose of MPA results in significant changes in some serum biochemical values in cats, although individual responses will vary.

Toxoplasma gondii inclusions in peripheral blood leukocytes of a red‐necked wallaby (Macropus rufogriseus)

A 2-year-old, male, red-necked (Bennett's) wallaby (Macropus rufogriseus) from a zoological facility was presented for peracute onset of severe depression, unresponsiveness, ataxia, and loose feces. Serum biochemical abnormalities included azotemia, hypoalbuminemia, increased alanine aminotransferase activity, hyperbilirubinemia, hyperphosphatemia, and hyperkalemia, consistent with multi-organ system failure. Severe thrombocytopenia suggested possible disseminated intravascular coagulation. Peripheral blood smear examination revealed numerous ovoid, protozoal inclusions within monocytes and occasionally within neutrophils. Despite aggressive supportive therapy, the patent died within 5 hours of presentation. Gross necropsy and histopathologic findings included severe multifocal necrotizing lesions in multiple organs. Numerous intralesional protozoal organisms were observed and were identified as Toxoplasma gondii by immunohistochemistry. Macropods (wallabies and kangaroos) are known to be highly susceptible to toxoplasmosis, with high mortality rates; diagnosis most often is obtained at necropsy. Detection of protozoal organisms in peripheral blood leukocytes is reported rarely and has not been documented previously in a macropod. Parasitemia in this case was attributed to severe, disseminated disease. Careful examination of peripheral blood smears in macropods suspected of toxoplasmosis may be warranted.

Serum biochemical abnormalities in goats with uroliths: 107 cases (1992–2003)

To characterize serum biochemical abnormalities in goats with uroliths. Retrospective case-control series. 107 male goats with uroliths and 94 male goats with various nonrenal diseases (controls). For male goats, results of serum biochemical analyses collected from 1992 through 2003 were retrieved from computerized records, as were signalment, clinical diagnoses, and discharge status. Results of analyses for BUN, creatinine, phosphorus, calcium, Na, K, Cl, total CO2, anion gap, and glucose were compared between goats with uroliths and control goats. Goats with uroliths had higher mean BUN, creatinine, total CO2, K, and glucose concentrations and lower mean phosphorus, Na, and Cl concentrations than control goats, with no difference in mean calcium concentration and anion gap. Goats with uroliths had higher frequency of azotemia, hypophosphatemia, hypochloridemia, and increased total CO2 and lower frequency of decreased total CO2 than control goats. Urolithiasis occurred more frequently in castrated males than in sexually intact males and in dwarf African breeds than in other breeds. Goats with uroliths often had hypophosphatemia at admission. Hypochloridemic metabolic alkalosis was the most common acid-base disorder. Rupture in the urinary tract system was associated with increased prevalence of hyponatremia and hyperkalemia. Clinicians should be aware of these abnormalities when determining fluid therapy.

A retrospective study of the clinical hematology and the serum biochemistry tests made on canine dirofilariasis cases in an animal hospital population in Bangkok, Thailand

Heartworm disease, caused by the filarial nematode, Dirofilaria immitis, is a major, potentially life-threatening disease of dogs, with worldwide distribution and global significance. It is not only of veterinary importance but it also has zoonotic potential in many regions. It is considered as an endemic disease in Thailand, although clinical data about the disease is rarely reported. The objectives of this study were to characterize the clinical hematology and the biochemistry of canine dirofilariasis cases admitted to Chulalongkorn University, Small Animal Teaching Hospital in Bangkok, Thailand, from 2001–2003. All hematology and serum biochemistry parameter interpretations were based on reference values. A total of 1023 dogs were evaluated in this study. Dogs were divided into three groups based on their heartworm classification (microfilaremic, occult and negative). The major hematological findings in microfilaremic dogs were a mild to moderate anemia, mild to severe thrombocytopenia, marked leukocytosis, moderate to marked neutrophilia, eosinophilia and monocytosis. The most common serum biochemical abnormalities in microfilaremic dogs included increased alkaline phosphatase, alanine aminotransferase and aspartate aminotransferase with a mean ± SD of 311 ± 299, 82 ± 76 and 50 ± 38 IU/L, respectively. It is likely that this parasitic infection led to the impairment of the hematological and biochemical status of the infected dogs. We believe that investigation of these laboratory based parameters, when associated with the clinical signs, is a very important approach to be considered in the routine clinical follow up, as well as being important for therapeutic evaluations.

Hypernatremia associated with intracranial B‐cell lymphoma in a cat

An 8-year-old, spayed female, domestic shorthair cat with a history of hyperthyroidism, anorexia, dehydration, cervical ventroflexion, and behavioral changes was referred to the Iowa State University College of Veterinary Medicine. The cat was obtunded, with severe dehydration (15%) and hypothermia (86 degrees F), and severe muscle atrophy and fasciculations. Serum biochemical abnormalities included severe hypernatremia (195 mmol/L, reference interval 155-165 mmol/L), hyperchloridemia (161 mmol/L, reference interval 123-131 mmol/L), and hypokalemia (3.6 mmol/L, reference interval 4.0-5.7 mmol/L). Calculated osmolality was 418 mOsm/kg (reference interval 280-305 mOsm/kg), attributable to the hypernatremia. The cat was kept warm and given fluid and glucocorticoid therapy and supportive measures but remained unresponsive. Hypernatremia and hyperosmolality improved through day 3, when the cat died suddenly. At necropsy, a 1.25-cm mass was found in the area of the thalamus and interthalamic adhesion that extended to the ventral aspect of the cerebrum. The histologic and immunohistochemical diagnosis was B-cell lymphoma. Hypernatremia and hyperosmolality in this cat were attributed to primary adipsia and hypothalamic dysfunction secondary to effacement of central nervous system tissue by neoplastic lymphocytes. To the authors' knowledge, this is the first reported case of central nervous system lymphoma, confirmed by use of immunohistochemical analysis as a B-cell phenotype, associated with hypernatremia. It also is the first reported case of lymphoma in animals limited to the thalamus, hypothalamus, and cerebrum, with no involvement of the spinal cord.

Rattlesnake Envenomation in 12 New World Camelids

Background: Rattlesnake envenomation of New World camelids is a seasonal problem with often dramatic clinical signs. Hypothesis: The purpose of this study was to identify the clinical signs, laboratory results, treatment methods, and outcome for rattlesnake envenomation in New World camelids. Animals: Medical records from 1988 to 2004 were searched for New World camelids presented for rattlesnake bite or clinical signs suspected to be related to recent envenomation. Twelve records were identified. Methods: From these records a retrospective study was performed. Results: Nine camelids presented for acute disease (2/9 arrived dead), whereas 3 presented for subacute onset of disease. Swelling of the lips, head and neck, tachypnea, dyspnea, tachycardia, and lethargy were the most common presenting signs. Snake bites were most commonly located to the muzzle (10/12). Common complete blood count (CBC) and serum biochemical abnormalities were neutrophilia, lymphopenia, increased muscle enzyme activity, hypoalbuminemia, hyperglycemia, hypokalemia, and thrombocytopenia. Treatment included combinations of intravenous fluid therapy, antimicrobials, anti‐inflammatory drugs, tetanus prophylaxis, tracheostomy, supplemental oxygen, antivenom, total parenteral nutrition, and nursing care. Five of the 10 animals with acute onset of clinical signs survived, and all animals with subacute presentation died. The mortality rate for New World camelids with severe local tissue reaction and systemic signs of envenomation was 58%. Clinical Importance: New World camelids that sustain rattlesnake envenomation and severe facial swelling precluding prehension and mastication have a guarded prognosis for survival. Aggressive treatment is recommended to optimize the chances of survival. Animals with less severe local tissue reaction and absence of systemic signs have a better prognosis.

Neurologic signs and hyperammonemia in a horse with colic

A 23-year-old Thoroughbred gelding was referred for the evaluation of acute onset of ataxia and depression, and a 2-day history of fever. On physical examination, the gelding was profoundly depressed and 10-12% dehydrated. The horse appeared very unstable, with a wide-based stance in the hind limbs, severe symmetric ataxia in all 4 limbs, and proprioceptive deficits in both hind limbs. Nasogastric intubation produced 4 L of brown, fetid reflux, and rectal examination revealed mild small intestinal and cecal distention. Hematologic abnormalities included neutropenia with toxic change, compatible with acute inflammation and endotoxemia, and prolonged coagulation times. Serum biochemical abnormalities included prerenal azotemia. metabolic acidosis, and electrolyte abnormalities consistent with enteritis. Blood ammonia concentration was markedly increased (406 micromol/L; reference interval 4-49 micromol/L), however, serum bile acids concentration and hepatic enzyme activities were within reference intervals. Histopathologic examination of a liver biopsy revealed no abnormalities and results of tests for several infectious agents were negative. Clinical signs resolved with correction of the dehydration and electrolyte abnormalities and with antibiotic therapy. The horse was diagnosed with hyperammonemic neuropathy associated with gastrointestinal disease. In such cases, hyperammonemia is caused by increased production of ammonia by organisms in the gastrointestinal tract in combination with increased gut permeability that facilitates ammonia absorption.

CHOLELITHIASIS IN FOUR CALLITRICHID SPECIES (LEONTOPITHECUS, CALLITHRIX)

Medical records of three male and three female callitrichids of four species (Leontopithecus chrysopygus, Leontopithecus rosalia, Callithrix argentata argentata, Callithrix kuhlii) diagnosed with cholelithiasis were reviewed. Ages of affected animals at the time of diagnosis ranged from 2-14 yr. Definitive antemortem diagnosis of cholelithiasis was made in four of the six cases. Chronic weight loss, lethargy, and weakness were seen in all cases. Chronic intermittent diarrhea was seen in three cases. Icterus and abnormal gait were each present in two of the animals. Hematologic and serum biochemical abnormalities included leukocytosis in five cases, elevated bilirubin (direct and indirect) in four cases, and anemia in four cases. Radiographic evidence of choleliths was observed in three cases. Surgical removal of choleliths was successfully performed on two animals. Full necropsies were performed on all cases, and choleliths were believed to contribute to morbidity in all cases. However, inflammatory bowel disease was determined to be the primary cause of weight loss and mortality in at least three animals. All choleliths analyzed were pigment stones, two being primarily composed of cystine.

Treatment for pancreatic abscesses via omentalization with abdominal closure versus open peritoneal drainage in dogs: 15 cases (1994–2004)

To compare survival rate, duration of hospitalization, and complications in dogs with pancreatic abscesses treated with omentalization with abdominal closure versus open peritoneal drainage and evaluate a pancreatitis severity score for potential prognostic value. Retrospective case series. 15 dogs with pancreatic abscesses. Data regarding species, breed, age, initial clinical signs, CBC, serum biochemical abnormalities, pancreatitis severity score, anatomic location of the abscess, intraoperative bacteriologic culture results, treatment modality, postoperative complications, outcome (dismissed alive from the hospital, died in the postoperative period, or euthanized at surgery), and duration of hospitalization were evaluated. 6 dogs survived, 6 dogs died or were euthanized after surgery, and 3 were euthanized during surgery. Five of 8 dogs treated with omentalization and abdominal closure survived, and 1 of 4 dogs treated with open peritoneal drainage survived. In several dogs, treatment required additional surgical procedures, which did not appear to affect outcome. Postoperative complications were similar among survivors and nonsurvivors. Mean duration of hospitalization for dogs treated with omentalization and abdominal closure was less than that of dogs treated with open peritoneal drainage. Neither pancreatitis severity score nor any individual components of the score were associated with outcome. Omentalization is a viable treatment option for pancreatic abscess in dogs. Furthermore, shorter hospitalization and better survival outcomes may make omentalization preferred over open peritoneal drainage.

Rattlesnake Envenomation in 12 New World Camelids

Rattlesnake envenomation of New World camelids is a seasonal problem with often dramatic clinical signs. The purpose of this study was to identify the clinical signs, laboratory results, treatment methods, and outcome for rattlesnake envenomation in New World camelids. Medical records from 1988 to 2004 were searched for New World camelids presented for rattlesnake bite or clinical signs suspected to be related to recent envenomation. Twelve records were identified. From these records a retrospective study was performed. Nine camelids presented for acute disease (2/9 arrived dead), whereas 3 presented for subacute onset of disease. Swelling of the lips, head and neck, tachypnea, dyspnea, tachycardia, and lethargy were the most common presenting signs. Snake bites were most commonly located to the muzzle (10/12). Common complete blood count (CBC) and serum biochemical abnormalities were neutrophilia, lymphopenia, increased muscle enzyme activity, hypoalbuminemia, hyperglycemia, hypokalemia, and thrombocytopenia. Treatment included combinations of intravenous fluid therapy, antimicrobials, anti-inflammatory drugs, tetanus prophylaxis, tracheostomy, supplemental oxygen, antivenom, total parenteral nutrition, and nursing care. Five of the 10 animals with acute onset of clinical signs survived, and all animals with subacute presentation died. The mortality rate for New World camelids with severe local tissue reaction and systemic signs of envenomation was 58%. New World camelids that sustain rattlesnake envenomation and severe facial swelling precluding prehension and mastication have a guarded prognosis for survival. Aggressive treatment is recommended to optimize the chances of survival. Animals with less severe local tissue reaction and absence of systemic signs have a better prognosis.

Therapeutic percutaneous ultrasound-guided cholecystocentesis in three dogs with extrahepatic biliary obstruction and pancreatitis

Three dogs were examined because of acute pancreatitis. In all 3, distension of the gallbladder was seen ultrasonographically, and extrahepatic biliary tract obstruction (EHBO) was diagnosed on the basis of ultrasonographic findings and serum biochemical abnormalities (i.e., high serum bilirubin and cholesterol concentrations and increased hepatic enzyme activities). In all 3 dogs, percutaneous ultrasound-guided cholecystocentesis (PUCC) was used to decompress the gallbladder, with cholecystocentesis performed multiple times in 1 dog. Serum bilirubin concentration was substantially decreased following the procedure in all 3 dogs. Two of the 3 dogs did not require surgery to resolve the obstruction. In the third dog, an exploratory laparotomy was performed because of concerns about development of abdominal effusion following the procedure. Bile staining of the mesenteric fat was seen during the laparotomy, but no defect in the gallbladder wall could be identified. In most dogs with EHBO secondary to pancreatitis, the obstruction resolves spontaneously as the acute pancreatitis improves so that surgery is not required. In those few dogs in which EHBO does not resolve or in which EHBO results in complications, therapeutic PUCC may be useful in relieving gallbladder distension.

INTRAHEPATIC PORTOSYSTEMIC VENOUS SHUNT IN A NEONATAL ROAN ANTELOPE (HIPPOTRAGUS EQUINUS COTTONI)

A 6-day-old, female roan antelope (Hippotragus equinus cottoni) was diagnosed with a single intrahepatic portosystemic venous shunt at necropsy. Clinical signs had included weakness, lethargy, hypothermia, diarrhea, and a weak suckle response. Multiple seizure episodes were associated with hypoglycemia and characterized by vocalization, muscle fasciculations, and disorientation. Hematologic abnormalities included anemia with hypochromasia, anisocytosis, poikilocytosis, and leukopenia with neutropenia and lymphopenia. Serum biochemical abnormalities included elevations in blood urea nitrogen and total serum bile acid concentration. A portosystemic vascular anomaly should be a differential diagnosis for nonthriving, exotic ruminant calves with overt or subtle neurologic signs, persistent hypoglycemia, and/or elevated bile acids. In very young calves, total bile acid concentration may be more useful in establishing a diagnosis than blood ammonia concentration.

Infarctive purpura hemorrhagica in five horses

Five horses were examined because of signs of muscle stiffness, colic, or both. All 5 had been exposed to Streptococcus equi within 3 weeks prior to examination or had high serum titers of antibodies against the M protein of S equi. Horses had signs of unrelenting colic-like pain and focal areas of muscle swelling. Four horses were euthanatized. The fifth responded to treatment with penicillin and dexamethasone; after 3 weeks of treatment with dexamethasone, prednisolone was administered for an additional 10 weeks. Common hematologic and serum biochemical abnormalities included neutrophilia with a left shift and toxic changes, hyperproteinemia, hypoalbuminemia, and high serum creatine kinase and aspartate transferase activities. Necropsy revealed extensive infarction of the skeletal musculature, skin, gastrointestinal tract, pancreas, and lungs. Histologic lesions included leukocytoclastic vasculitis in numerous tissues and acute coagulative necrosis resembling infarction. These horses appeared to have a severe form of purpura hemorrhagica resembling Henoch-Schönlein purpura in humans and characterized by infarction of skeletal muscles. Early recognition of focal muscle swelling, abdominal discomfort, neutrophilia, hypoalbuminemia, and high serum creatine kinase activity combined with antimicrobial and corticosteroid treatment may enhance the likelihood of a successful outcome.

Dysphagia as the primary clinical abnormality in two dogs with inflammatory myopathy

Two adult Boxers were evaluated because of chronic dysphagia of several years' duration. Serum creatine kinase activity was high in both dogs, but other hematologic or serum biochemical abnormalities were not detected. Esophagraphy revealed abnormalities of the cricopharyngeal phase of swallowing in both dogs, and electromyography of the pharyngeal and laryngeal muscles revealed complex repetitive discharges, positive sharp waves, and fibrillation potentials characteristic of primary myopathy or neuropathy. Because of the severity of their condition, both dogs were euthanatized. Histologically, mixed-cell infiltrates were seen in sections of the masseter and thyropharyngeal muscles. Results of indirect immunofluorescence staining for proteins associated with dystrophic myopathy were unremarkable, except for decreased staining for integrin alpha7. A diagnosis of chronic inflammatory myopathy was made. The clinical importance of reduced staining for integrin alpha7 could not be determined but was considered to be a result of the myopathy.

Hematologic and biochemical abnormalities indicating iron deficiency are associated with decreased reticulocyte hemoglobin content (CHr) and reticulocyte volume (rMCV) in dogs

The ADVIA 120 automated hematology system uses low- and high-angle light scatter to determine individual RBC and reticulocyte volume and hemoglobin (Hgb) concentration. Current hematologic and biochemical markers of iron status in the dog are insensitive, and results may be highly variable, especially in the presence of concurrent disease (ie, inflammation, neoplasia). Reticulocyte Hgb content (CHr) has proven useful in detecting early iron deficiency and iron deficiency masked by concurrent disease in human patients. The purpose of this study was to retrospectively investigate the association of low CHr and reticulocyte MCV (rMCV) with hematologic and biochemical abnormalities indicative of iron deficiency in canine patients. Reference intervals for CHr and rMCV were established on a population of 362 hematologically-normal dogs using standard methods. CBC and serum biochemical results from 833 dogs at Colorado State University Veterinary Teaching Hospital were retrospectively evaluated. The prevalence of decreased CHr and rMCV values was determined based on the reference intervals. Hematologic (HCT, MCV) and biochemical (serum Fe concentration, percent saturation of transferrin [% sat]) values were compared among dogs with low CHr (n=58), low rMCV (n=50), and control dogs (cohort groups from the initial population) using a Fisher exact test. Reference intervals were 22.3-27.9 pg for CHr and 77.8-100.2 fL for rMCV. Seven percent (n=58) of dogs in the hospital population had low CHr and 6% (n=50) had low rMCV based on the reference values. Dogs with low CHr had significantly lower HCT, MCV, serum Fe, and % sat values than did control dogs. In addition, dogs with low CHr or low rMCV values had a higher frequency of microcytosis, anemia, low serum Fe concentration, and low % sat than did control dogs. Low CHr and low rMCV are associated with hematologic and serum biochemical abnormalities indicative of iron deficiency. CHr and rMCV hold promise as noninvasive, cost-effective measures of iron status in the dog.