"Patil flew to Mumbai on Wednesday and got admitted to a private hospital for treatment after he complained of chest pain and breathing," a party source told here.
Patil, a lawmaker from Kagwad Assembly segment in the state's northwest Belgaum district, was staying with the party's other legislators at a resort near Devanahalli on the city's northern outskirts.
"We learnt about his absence from the resort earlier in the day and came to know on enquiry that he flew to Mumbai for treatment," the source said on condition of anonymity.
With Patil absenting from the session, the ruling ally's strength in the Assembly is 66, including the Speaker and senior 'rebel' legislator R. Ramalinga Reddy, who is present in the House after withdrawing his resignation from the Speaker.
With 12 rebel Congress and three Janata Dal-Secular (JD-S) legislators not present in the House, the strength of the ruling combine is 101, including one from the Bahujan Samaj Party (BSP).
With the overall strength of the Assembly reduced to 110 from 225, including the nominated member without voting right, the new halfway mark is 106 for simple majority.
The opposition Bharatiya Janata Party (BJP) has 107, including two Independents to defeat the Congress-JD-S coalition government when the confidence motion is put to vote after the day-long debate.
( With inputs from IANS )