Feline constipation is a common and clinically challenging condition that extends beyond a simple motility disorder, involving complex systemic metabolic and acid–base disturbances. The findings of the present study demonstrate that constipated cats exhibit significant alterations in multiple hematological, biochemical and blood gas parameters, supporting the view that constipation should be approached as a systemic condition rather than a localized gastrointestinal problem. This comprehensive evaluation provides valuable insights into the pathophysiological mechanisms underlying feline constipation and offers evidence-based guidance for clinical management.
The clinical signs observed in the constipated cats, including tenesmus, passage of dry feces, anorexia and lethargy, were consistent with previous reports (
Defarges, 2010;
Jugan, 2022). Clinical scoring was performed using a standardized scale (0-4) and the scores progressively declined over the treatment period, indicating a consistent clinical improvement across all groups (Table 1). The most pronounced and rapid improvement was observed in the lactulose (LT) and psyllium (PHF) groups, suggesting that these agents provide more consistent clinical benefits. This finding aligns with the established mechanisms of action of these laxatives, which promote gradual and physiological colonic hydration and softening of fecal material (
Chandler, 2008;
Tams, 2013). In a similar context,
Lakpale et al. (2003) emphasized the importance of balanced nutrient and fiber supplementation in improving gastrointestinal function and overall clinical outcomes in small animals, while
Shukla et al. (2013) demonstrated that integrated nutritional approaches significantly enhance the efficacy of laxative therapy, further supporting the superior outcomes observed with psyllium and lactulose in the present study. These observations highlight the value of combining appropriate laxative selection with nutritional support to achieve optimal clinical results.
No statistically significant differences were observed in body temperature, heart rate, or respiratory rate between the groups or across time points (Table 2), indicating that the systemic inflammatory and metabolic disturbances associated with constipation did not manifest as overt vital sign abnormalities. This suggests that while constipation is associated with significant metabolic alterations, these may not be readily apparent through routine physical examination alone, underscoring the importance of laboratory monitoring. The stability of vital signs across all treatment groups further confirms the safety of the evaluated laxative protocols and supports their clinical applicability.
Hematological analysis at baseline (T0) (Table 3) revealed significantly elevated WBC counts, indicating an inflammatory response, which is consistent with the systemic inflammatory state associated with prolonged fecal retention (
Adams et al., 2014). Increased RBC, hemoglobin and hematocrit values were also observed, reflecting hemoconcentration secondary to dehydration. These findings are in agreement with those of
Willard and Tvedten (2015), who reported similar hematological alterations in constipated cats. Following treatment, these parameters progressively returned toward normal values, particularly in the PHF and LT groups, suggesting that effective management of constipation not only alleviates clinical signs but also corrects dehydration and hemoconcentration. This highlights the importance of monitoring hematological parameters during the treatment of feline constipation to ensure adequate rehydration and resolution of systemic inflammation. The superior hematological recovery observed with lactulose and psyllium underscores their role in restoring systemic homeostasis.
Biochemical analysis (Table 4) demonstrated elevated liver enzyme activities (ALT, AST) and renal markers (BUN, creatinine) at T0, indicating systemic metabolic stress. These changes may be associated with increased absorption of bacterial metabolites and endotoxins from retained fecal material, as well as reduced renal perfusion secondary to dehydration (
Center, 2005;
Hall et al., 2017). The gradual decline in these parameters by Day 3 suggests progressive recovery of metabolic function, particularly in the LT and PHF groups. These findings underscore the importance of evaluating biochemical parameters in constipated cats to detect and monitor systemic metabolic disturbances. Moreover,
Pingoliya et al. (2014) reported that metabolic stress markers are closely associated with the severity of gastrointestinal dysfunction in animals and that timely correction of these parameters is crucial for preventing long-term organ damage. Similarly,
Kumbhare et al. (2014) demonstrated that systematic monitoring of biochemical parameters significantly improves the prognosis in animals with gastrointestinal disorders. The progressive improvement in liver and renal markers observed in the present study supports these findings and highlights the systemic impact of constipation, while also confirming the therapeutic value of appropriate laxative selection.
Blood gas analysis (Table 5) confirmed the presence of metabolic acidosis at T0, characterized by decreased pH and bicarbonate levels. This condition is likely related to the accumulation of acidic microbial metabolites and impaired tissue perfusion (
Kaplan and Frangos, 2005;
Wilson et al., 2015;
Suchodolski, 2011). Partial correction was observed at Day 1, while Day 3 values indicated progressive improvement, demonstrating the effectiveness of the treatment protocols in restoring acid–base balance. The resolution of acidosis was notably more consistent in the LT and PHF groups, suggesting that these agents facilitate more stable metabolic recovery. This finding is particularly important, as metabolic acidosis can have deleterious effects on multiple organ systems if left uncorrected.
Electrolyte imbalances, particularly involving potassium dynamics, were also observed in the present study. At T0, constipated cats exhibited significantly elevated potassium levels, which gradually declined toward normal values following treatment. However, magnesium sulfate (MS) and sennoside-bisacodyl (SBC) were associated with transient electrolyte fluctuations, particularly affecting potassium balance. These findings are consistent with previous reports indicating that stimulant and saline laxatives may cause significant electrolyte disturbances, especially when used at higher doses or in dehydrated patients (
Chandler, 2008;
Tams, 2013). Magnesium sulfate, despite its common use in some clinical settings (
Chandler, 2008), was found to be associated with transient electrolyte disturbances in our study. This finding underscores that while it may be used, it is not the safest option compared to lactulose or psyllium, which provide more stable metabolic outcomes. Therefore, clinicians should exercise caution when using these agents and consider more gradual and physiologically compatible alternatives, such as lactulose and psyllium, particularly in patients with pre-existing electrolyte imbalances or renal compromise.
Among the treatment groups, lactulose (LT) and psyllium (PHF) demonstrated superior outcomes in terms of both clinical improvement and metabolic stabilization. This may be attributed to their more gradual and balanced effects on intestinal hydration, luminal softening and colonic motility. Lactulose, an osmotic laxative, works by increasing water content in the colon through osmotic action, thereby softening feces and stimulating peristalsis (
Tams, 2013). Psyllium, a bulk-forming laxative, absorbs water and increases fecal bulk, promoting natural bowel movements without causing significant electrolyte shifts (
Chandler, 2008). These mechanisms explain the more stable metabolic outcomes observed with these agents in the present study and support their recommendation as first-line agents in the management of feline constipation. The integration of nutritional strategies, as highlighted by
Lakpale et al. (2003) and
Shukla et al. (2013), further enhances the therapeutic potential of these agents.
In contrast, magnesium sulfate (MS) and sennoside-bisacodyl (SBC) were associated with transient electrolyte disturbances, particularly affecting potassium balance. Magnesium sulfate, a saline laxative, draws water into the intestinal lumen through osmotic action but may also cause significant electrolyte losses, particularly in dehydrated patients (
Chandler, 2008). Sennoside-bisacodyl, a stimulant laxative, increases colonic motility but may also cause abdominal cramping and electrolyte imbalances, especially with prolonged use (
Tams, 2013). These findings suggest that while these agents may be effective in alleviating clinical signs, their use should be carefully monitored and they should be avoided in patients with pre-existing electrolyte imbalances or renal compromise.
Intermediate measurements (Day 2) showed minor variations and did not significantly alter the overall trend observed between Day 1 and Day 3; therefore, these data were not included in the tables to improve clarity.
The findings of the present study have important clinical implications. First, they emphasize that feline constipation should be approached as a systemic condition rather than a purely gastrointestinal disorder. Comprehensive evaluation of hematological, biochemical and blood gas parameters is essential for accurate assessment of disease severity and for monitoring treatment response. Second, the results suggest that lactulose and psyllium are the preferred agents for managing feline constipation, as they provide consistent clinical improvement without causing significant metabolic disturbances. Third, the use of magnesium sulfate and sennoside-bisacodyl should be approached with caution, particularly in patients with dehydration or electrolyte imbalances. The integration of nutritional and metabolic monitoring, as advocated by
Pingoliya et al. (2014) and
Kumbhare et al. (2014), further strengthens the clinical approach to managing this condition.
